A Larix gmelinii forest planted in 2004 at Maoershan, Xiaoxing'an Mountain, China was taken as study materials. In 2012, the Larix gmelinii forest was divided into three plots and four removal precipitation treatments in each 25 m×25 m plot: 100% rainfall removed, 50% rainfall removed, snow removal and control. To observe the effect of decreasing precipitation on radial growth of Larix gmelinii in cellular scale, the radial length and quantity of expansion cells were measured by using paraffin section method with micro increment borer in early June and late August. Tree-ring cores were extracted by increment borer in October, and the radial length and quantity of mature tracheids were measured to identify the impact of decreasing precipitation on Larix gmelinii radial growth. The results showed that the radial growth of Larix gmelinii significantly positively correlated with monthly mean temperature at growing season, and negatively correlated with monthly total precipitation at the end of growing season. In terms of three plots taken together, the number of mature tracheids in snow removal treatment was the largest, followed by the control treatment, and then in 50% and 100% rainfall removal treatment. Radial length of mature tracheids, however, did not show significant difference among four treatments. Whereas the number and radial length of mature tracheids among three plots were significantly different. In plot 1, the number of mature tracheids in 100% and 50% rainfall removal treatment, snow removal treatment and control increased with the increasing of soil moisture, but the radial tracheid length did not show obviously difference. In plot 2, the radial length of mature tracheid in snow removal treatment was significantly smaller than those in other three treatments, while the radial length of mature tracheid in 50% and 100% rainfall removal treatments were not significantly different with that in control treatment. In plot 3, there was no significant difference in the radial length of mature tracheid among four treatments, except the radial length of mature tracheid in 100% rainfall removal treatment was slightly smaller than that in other three treatments. It could be caused by lots of shade and higher soil moisture in plot 3. The data of paraffin was to investigate the effects of decreasing precipitation on the number of cambium cell division and radial length from the cambium cells that expand in June and August. At the beginning of decreasing precipitation (in June), the number of expansion cells in plot 3 was decreased with the decrease of soil moisture among different treatments. At the end of decreasing precipitation (in August), the number of expansion cells in plot 1 was decreased with the decrease of soil moisture among four treatments. Our results indicated that the decrease of precipitation will produce a significant impact on radial growth of Larix gmelinii in Maoershan, while the extent of the influence is determined by the microenvironment of tree growth. In addition, the effects of decreasing precipitation in different seasons on Larix gmelinii radial growth are significant differences.