Direct competitive inhibition enzyme-linked immunosorbent assay for determination of fumonisin B1 (FB1) in corns were developed by using anti-FB1 monoclonal antibody. The minimum detectable concentration of FB1 was 10 ng/ml, and the standard curve was linear between 10 ng/ml and 5 micrograms/ml. The FB1 concentration of some corn samples from Xinjiang, Anhui, Hilongjiang provinces and Haerbin city were detected. The result imply that 34 out of 156 samples were positive for FB1. The concentrations were in the range of 0.18-31.32 micrograms/g. The average concentration was 12.04 micrograms/g.