In this thesis, effects of common factors in yeast extract production with autolysis on yield and total amount of amino acid nitrogen in supernatant, degradation of RNA and saccharides during autolysis were studied, in which fresh baker's yeast was used as material. Extraction of 5'-phosphodiesterase from barley rootlets was also studied. The optimum technology conditions of yeast extract production was determined by comprehensive considering results of above-mentioned study. In addition, yeast cell wall polysaccharide (CWP) was extracted from yeast waste after autolysis. Emulsifying property and acetylated modification of CWP were also studied. The following results were achieved.Improvement of yield and total amount of amino acid nitrogen in supernatantStudy on improving yield and total amount of amino acid nitrogen in supernatant showed that high pressure homogenization, adding external papain and yeast extract as autolysis promotor could improve yield and total amount of amino acid nitrogen in supernatant and shorten producing time. Effects of different homogenization pressure and times were different, suitable homogenization condition was two times under 45 Mpa. pH, temperature, amount and adding time of papain, autolysis duration could affect autolysis with external papain to some extent, and the optimum technology conditions were that papain was added by 10×10~4u per kg autolyzed solution at 6 hours after autolysis beginning, pH was adjusted to 6.0, then autolyzed at 55℃ for 26 hours. Suitable adding amount of yeast extract was 0.4 percent of autolyzed solution. Contrasted with no mixing and continuous mixing, intermittent mixing was advantageous to improving yield and total amount of amino acid nitrogen in supernatant, and contrasted with one time of centrifugation, effect of more times of centrigutation was better.Degradation of RNA during autolysisStudy on degradation of RNA during autolysis showed that, degradation of RNA was firstly increased slowly, then increased very fast, finally tented towards balance gradually. Total amount of 5'-GMP and 5'-IMP in supernatant was firstly increased