In this study,the bacteria from the mud in tidal-flat Sinonovacula constricta aquaculture area were isolated each month from March to December,2002,and the temporal and spatial distribution of heterotrophic bacteria,ammonifying bacteria,denitrifying bacteria,and sulphate reducing bacteria were analyzed.The results showed that all the 515 isolated bacteria mainly belonged to 1 family and 13 genera.The bacterial flora in different layers of the mud was almost consistent,while the composition was different.The predominant genera were Clostridium,Bacillus,Corynebacterium,Photobacterium,and some Enterobacteriaceae.The number of heterotrophic bacteria in the surface layer and the bottom fluctuated in 7.6×10~3 cfu·g~(-1)～2.0×10~5 and 1.6×10~3～1.0×10~5 cfu·g~(-1),ammonifying bacteria fluctuated in 1.5×10~6～9.0×10~7 and 9.0×10~5～1.0×10~7 cfu·g~(-1),denitrifying bacteria fluctuated in 9.0×10~3～4.0×10~6 and 5.0×10~2～1.9×10~6 cfu·g~(-1),and sulphate reducing bacteria fluctuated in 5.0×10~4～5.0×10~6 and 1.9×10~4～2.0×10~6 cfu·g~(-1),respectively.The detection rates of ammonifying bacteria,denitrifying bacteria and sulphate reducing bacteria in the mud were all 100%,and these bacteria increased significantly in the second half of the year,indicating that the environment of the Sinonovacula constricta aquaculture area was deteriorated due to the accumulation of NH_3,nitrite and H_2S,and it is important to regulate the breed capacity and redistribute the breeding environment. In this study, the bacteria from the mud in tidal-flat Sinonovacula constricta aquaculture area were isolated each month from March to December, 2002, and the temporal and spatial distribution of heterotrophic bacteria, ammonifying bacteria, denitrifying bacteria, and sulphate reducing bacteria The results showed that all the 515 isolated bacteria mainly belonged to 1 family and 13 genera.The bacterial flora in different layers of the mud was almost consistent, while the composition was different. The predominant genera were Clostridium, Bacillus, Corynebacterium, Photobacterium, and some of Enterobacteriaceae. The number of heterotrophic bacteria in the surface layer and the bottom fluctuated in 7.6 × 10 ~ 3 cfu · g -1 ~ 2.0 × 10 ~ 5 and 1.6 × 10 ~ 3 ~ 1.0 × 10 ~ 5 cfu · G ~ (-1), ammonifying bacteria fluctuated in 1.5 × 10 ~ 6 ~ 9.0 × 10 ~ 7 and 9.0 × 10 ~ 5 ~ 1.0 × 10 ~ 7 cfu · g -1, denitrifying bacteria fluctuated in 9.0 × 10 ~ 3 ~ 4.0 × 10 ~ 6 and 5.0 × 10 ~ 2 ~ 1.9 × 10 ~ 6 cfu · g ~ (-1), and sulphate reducing bacteria fl uctuated in 5.0 × 10 ~ 4 ~ 5.0 × 10 ~ 6 and 1.9 × 10 ~ 4 ~ 2.0 × 10 ~ 6 cfu · g ~ (-1), respectively. These detection rates of ammonifying bacteria, denitrifying bacteria and sulphate reducing bacteria in the mud were all 100%, and these bacteria increased significantly in the second half of the year, indicating that the environment of the Sinonovacula constricta aquaculture area was deteriorated due to the accumulation of NH_3, nitrite and H_2S, and it is important to regulate the breed capacity and redistribute the breeding environment.