Theory of mind (ToM), as an important competence of children's social cognition, shows a striking development in the preschool period. There is a shift from the age of 3 to 5 in children's success on ToM tasks. One potentially important factor, which might affect both the emergence and expression of ToM, is executive function (EF). Inhibitory control (IC), as the kernel of EF, is the focus of the research for many researchers in this field. Ever since the 1990's, a large quantity of researches into the relationship between ToM and EF, both empirically and theoretically, have been conducted by developmental psychologists abroad. This has made it one of the most active and important research fields in the development of children's social cognition. This research attempts to explore the relationship between ToM and EF (major component is IC) in 3- to 4-year-old children. It will help us to understand the inner mechanisms and individual differences in children's development of ToM. Meanwhile it can provide us the theoretical guide on how to foster children's ToM competence, improve their social communication skills and treat autism and attention deficit hyperactivity disorder.In this thesis, first, a comprehensive review is made on the important empirical findings and major theoretical models concerning the development of children's ToM, EF (especially IC), and the relationship between ToM and EF within two decades abroad. Then a brief description of two major theoretical orientations towards preschoolers' difficulties on ToM tasks (conceptual deficit and EF) is made. Five competing theories on the EF-ToM relationship, their relevant evidence and evaluation are discussed. Finally it is proposed that it is feasible to train children's ability of ToM and EF. A critical analysis on current researches and problems concerning this area is also made. A limitation of the previous researches of ToM-EFrelationship is that the designs are most cross-sectional or short-term longitudinal ones. Due to this, all designs cannot clarify the issue of cause-effect problems. It can be noted that to evaluate the causal factors in children's psychological understanding, children must be exposed in the information of mental states through experimental operations. Based on this point of view, two researches are conducted: One is a correlational study, and the other is a training study.The purpose of the first study is to explore whether 3 or 4 year-old children's ToM has some correlations with EF. Children's performance was measured on a lot of tasks such as ToM, IC, non-mental state and intelligence. The major findings are as follows:First, the performance of 4 year-old children on ToM tasks is much better than that of 3 year-old children. There are correlations between ToM and intelligence, and also between ToM and non-mental state tasks. But there is no significant difference between the male and female. There are correlations among ToM tasks. These correlations are still robust even if such factors as age, gender, intelligence and non-mental state tasks are controlled. Second, the performance of 4 year-old children on IC tasks is superior to that of 3 year-old children, but there is no significant difference between the male and female. However, there is a strong correlation between IC and intelligence. There are correlations among IC tasks and these correlations are still robust even if such factors as age, gender, intelligence and non-mental state tasks are controlled. Third, children's performance on ToM tasks and on IC tasks are closely connected with each other ( r=.73, p<.001). This correlation still exists even if such factors as age, gender , intelligence (including Verbal IQ and Performance IQ) and non-mental state control tasks are controlled.The goal of the second study is to explore the cause-effect relationship between young children's ToM and EF. This study is composed of two training experiments: one is ToM training (e.g., belief training and coherence training) in which the influences of ToM on the development o