Radio occultation technique for the Earth's atmospheric profiling, a new application of the Global Navigation Satellite Systems, is one of the most advanced space exploring techniques in the 21st century. This technique can measure the profiles of meteorological fields of the neutral atmosphere and the electron densities of the ionosphere with high precision and high vertical resolutions. It can operate all-weather with long-term stabilities and global coverage. The global-distributed occultation data will have a huge promotion on the numerical weather prediction, climate and space weather researches.This thesis focuses on some aspects of the radio occultation technique and its applications. The main works can be summarized as following:1. With the three-dimensional ray-tracing program, the simulation of LEO-GPS occultation is given. The radio path of occultation observation is simulated, and then the excess phase delay is calculated. This work can be used for studying the effects of the neutral atmosphere and ionosphere on the occultation observations and evaluating the performance of the inversion techniques.2. The inversion techniques of occultation data are described and discussed in details. Taken GPS/MET observations as examples, the atmospheric parameters profiles are retrieved accurately.