A test was conducted on a liquefied natural gas (LNG) turbocharged engine in the transient process of low-speed working condition.By secondary treating the measured transient cylinder pressure curve, various combustion state parameters were obtained.On this basis, the internal relation among these transient combustion characteristic parameters and the effect of these parameters on LNG engine performances were analyzed.The results have shown that the variation range of 50% of the burnt point with the cycle number is about 5 oCA, and its fluctuation is mainly caused by the change of the combustion starting point.The peak values of 50% of the burnt point correspond to those of the combustion starting point, and so do the valley values.The peak values of 50% of the burnt point correspond to the valley values of maximum pressure rise rate and maximum cylinder pressure, whereas the opposite is true.The variation range of 10%~90% of the combustion duration is 30~45 oCA, and the rise of combustion duration becomes one of the main reasons for the decline of LNG engine IMEP (indicated mean effective pressure) and NMEP (net mean effective pressure).The fluctuations of combustion characteristic parameters are mainly caused by the instability of the combustion start point.To precisely control the combustion start point becomes an effective way to ensure that LNG engine has good transient performances at low speed and high intake pressure working condition.