Compared with diesel engine with the equivalent displacement, high pressure direct injection natural gas engine ignited by a small quantity of diesel has lower emission and comparable thermal efficiency, which has a promising prospect. For this kind of NG engine, the previous extensive studies mostly focused on the combustion and emission characteristics and the study on the cyclic variation which has significant effects on the stability of engine operation was very limited. The cyclic variations of different operating parameters were investigated at full load on a high pressure direct injection natural gas engine ignited by a small quantity of diesel. The results indicated that the cyclic variation of peak cylinder pressure first increases and then decreases with the increase of natural gas injection timing and tends to be higher at low speed. The cyclic variations of ignition delay and 50% mass burnt fraction (50%MBF) increase with the injection advancement and the increase of engine speed. The cyclic variation of indicated mean effective pressure (IMEP) increases with the injection timing at 24 MPa, but the changing law relates to engine speed at 30 MPa. In addition, the cyclic variation of IMEP is relatively high at high speed and that of each parameter is little affected by injection pressure.