To explore the relationship between larch caterpillar population and meteorological factors, a suite of linear regression models were developed. We used a stepwise regression approach to obtain the best model based on the Akaike information criterion (AIC). We also identified the key meteorological factors based on relative weight,and analyzed their marginal influences on larch caterpillar population. Our modeling results showed that meteorological conditions during the young larva stage and breeding stage played a key role in impacting larch caterpillar population. In contrast, meteorological conditions during the middle larva stage and old larva stage had a weaker effect. The mean daily relative humidity during young larva stage,the accumulated daily temperature less than -22 ℃ during young larva's overwintering stage,and the total rainfall in breeding stage were the key meteorological factors affecting the population of larch caterpillar. With the increase of one standard deviation from the mean daily relative humidity during young larva stage and the total rainfall in breeding stage,the larch caterpillar population would be reduced by 62% and 35% of standard deviation,respectively. In contrast,one standard deviation increase of the accumulated daily temperature less than -22 ℃ during young larva's overwintering stage would increase larch caterpillar population by 40% of standard deviation. Our study suggests that the larch caterpillar population in the future may explode in response to global warming,and its infestation could exhibit a new pattern. It is therefore very important to establish a long-term population monitoring system.