Abstract: Abstract: The organic waste mainly refers to the solid waste that is generated by residents' daily life. If the organic waste is converted into energy through anaerobic digestion, it will reduce the adverse impact on the environment and contribute to reduction in consumption of fossil fuel. Analysis of the space and time differences of various kinds of microbial community in fermentation process, plays a very important role for controlling the fermentation process effectively, understanding the fermentation stage, optimization of fermentation conditions and improving the efficiency of biogas production. This paper investigated the temporal and spatial distribution of microbial community during the semi-dry fermentation of organic waste, and studied the relationship of acid production, methane production and ammonia production using most probable number (MPN). The experiment used anaerobic fermentation under one-time charging medium temperature (37℃), and designed six sampling positions. The inoculum was biogas slurry fermented with pig manure, and the concentration was 30%, pH value was adjusted to 7.0 before anaerobic fermentation. The results showed that, in the early stage of organic waste anaerobic fermentation, large amounts of air existed in the reactor, and there was less number of anaerobic bacteria. With the formation of the anaerobic environment and rich nutrients, the number of anaerobic bacteria began to rise. The anaerobic acidification bacteria and anaerobic ammonification bacteria proliferated earliest, and the acidification bacteria was prior to reach maximum than ammonification bacteria and occupied the dominant position. The methane bacteria didn't proliferate at the start-up phase, they enter the fast growth stage after 15 days, and the peak value was 3.24×109 mL-1 on the 25th day. In the gas peak decline period, the number of anaerobic ammonification bacteria and anaerobic acidification bacteria began to decline, however, the methane bacteria number kept on the order of magnitude in the whole period. The anaerobic cellulose-decomposing bacteria grew slowly, and the number was only 106 mL-1 on the 45th day. In the space, numbers of anaerobic acid bacteria and methane bacteria in the central part were more than those at the edge, and the numbers in the bottom were more than on the top; the most number of anaerobic ammoniation bacteria grew in middle edge and center position; at the same height, the numbers of edge position were more than the center position basically. The anaerobic cellulose-decomposing bacteria began to proliferate in the bottom. The number of the anaerobic bacteria on the top was lower than other places, due to the residual air on the top that was not conducive to the growth of anaerobic bacteria. In the reactor design, intermediate feed may be given priority to, edges feed was complementary, which was conducive to make full use of fermentation materials, and to improve the efficiency of the reactor. The dynamic model of anaerobic acidification bacteria and methanogens distribution differences was constructed preliminarily, and the correlation coefficients of fitting model were 0.824 and 0.939, respectively. The established model could predict effectively, and could provide the appropriate reference value of semi-dry anaerobic fermentation technology. The applicability of the model still requires further test to verify, therefore, the reactor enlarged gradually can be used for further study and parameters correction. This paper has theoretical significance for the technological processes of biogas production from organic waste.