Abstract: A simulation system was constructed to investigate effect of withering of Cyanobacteria bloom on abundance and community compostition of ammonia-oxidizing bacteria (AOB) in surface sediments.The system consisted of three treatments, i.e. (1) CK, (2) addition of lab-cultured Cyanobacteria and (3) addition of wild Cyanobacteria collected from a lake. Abundance, community composition and diversity of AOB were analyzed with the real-time qPCR and molecular biological methods, like clone library, etc.. Results show that (1) Treatments 2 and 3 were much higher than Treatment 1 in abundance and community diversity of AOB; (2) N. oligotropha group of Nitrosomonas was the dominant AOB group, accounting for approximately 75% of the total AOB community in the surface sediments; and (3) Compared to Treatment 1, Treatments 2 and 3 were found to have some new AOB groups, such as N. communis and Nitrosospira. The findings indicate that N.oligotropha is absolutely the dominant group in all the treatments, and withering of Cyanobacteria bloom may improve AOB in the surface lake sediments in both abundance and diversity.