The morphological characteristics of gully erosion are the key factors to understand the occurrence and development of gully erosion, which are regarded having the great significance to explore the variation characteristics of gully morphology parameters in different seasons for in-depth understanding of the erosion process of gully erosion and its governance. In this study, three erosion gullies in Guangrong small watershed of Hailun City, Heilongjiang Province were selected as the research objects to explore the differences in the length, area, volume and other morphological parameters of erosion gully under seasonal changes. The results showed that: (1) The cross-sectional morphology of erosion gullies changed from "V" shape to "U" shape from the head to the tail in different seasons; (2) The length increase of erosion gullies caused by the gully advance and the gully tail retreat during the rainfall period was greater than that caused by the gully advance during the snow melt period; (3) The increase of erosion gully area in the precipitation period was greater than that in the snow melt period, but the changes of erosion gully area in different periods were different. The increase of erosion gully area in the precipitation period was mainly caused by the change of gully length and the large-scale collapse around the gully head, while the increase of erosion gully area was caused by the change of gully length and the expansion of gully bank in the snow melt period; (4)The variation of gully volume in the precipitation period was greater than that in the snow melt period, which was related to the variation of gully length, area and the shearing capacity of runoff. The undercut gully erosion capacity of runoff generated by rainfall in the precipitation period was greater than that generated by snow melt runoff in the snow melt period. The results can provide theoretical bases for the prevention and control of gully erosion.