Abstract: Hydrocracking catalyst containing small crystal size zeolite Y was prepared and its hydrocracking performance processing heavy oil was studied using a single stage device with two fixed-bed reactors in series. The effects of reaction temperature, liquid hourly space velocity (LHSV) and nitrogen content of hydrotreated feed on the cracking performance of catalyst were investigated, as well as the stability of catalyst was examined. Results showed that under the same reaction conditions, compared with conventional zeolite Y catalyst, using small crystal size zeolite catalyst the conversion of feed could be higher 3.5 percentage points. Results also showed that with the increase of reaction temperature, the conversion of feed increased; under constant conversion, the effect of LHSV on product distribution and product quality was little; the increase of nitrogen content in hydrotreated feed had negative effect on product yield and quality. During the long-term stability test, from 360 h to 2 160 h, the reaction temperature only increased 2 oC, and the distributions of products basically unchanged, which indicated that the operation stability of small crystal size zeolite Y catalyst was excellent.