For the sake of extracting the faultc haracters of crankshaft bearing of diesel engine, the method of bispectral analy sis was adopted. Bispectral characteristic plane in frequency field was brought forward to characterize the data. By bispectral analyzing of the vi bration data and searching the field of bispectral modulus, characteristic planes in data were found out. The result shows that the best places for data collect ion are the both sides of engine where the crankshaft is located. The best rotat ional speed of engine is above 1800 r／min. The area besides the diagonal contains many fault characteristics. The noise can be reduced and characteristics in vibration data of the crankshaft bearing can be extracted efficiently by the method of bispectr al analysis.