Abstract: A large area of lateritic paddy field covers the south of China. One of its basic features is poor fertility with low amount of organic matter, insufficient and imbalanced available nutrition. A series of field, pot experiments and laboratory analysis showed that, the dynamics(accumulation and decomposition)of organic matter in lateritic paddy field has not gotten equilibrium in the high temperature and rainy subtropical area. A succesive 4-year in situ trial treated by different amounts of organic manure showed that the accumulation of soil organic matter is more rapid than that of decomposition and the content of organic matter tends to be raised with the amount of organic manure application, meanwhile, composition of humus has been improved. However, organic manure application can lead to the fluctuation of ecosystem in paddy soil, speed up the reduction process, reduce redox potential, promote the production of reducing matter and decrease pH value in a short duration, this effect will be relaxed if lime is incorperated simultanously.