[Objective] The morphological characteristics and influencing factors of a gully head in a typical agricultural watershed in the rolling-hill black soil region of Northeast China were studied in order to provide basic data and theoretical support for controlling gully erosion in a mollisols region. [Methods] The study was conducted for gully heads of a typical agricultural watershed in Hainan Township, Hailun City, Heilongjiang Province. The morphological characteristics of the gully heads, soil type, and soil configuration were investigated in the field. The correlation between gully heads morphological characteristics and internal causes (soil characteristics) and external environmental factors were analyzed. [Results] ① At Hainan Township small watered the soil types of the cut gully head were typical black soil, meadow black soil, and alluvial soil. The soil structure consisted of mainly humus layer (A) + illuvial layer (B) + parent material layer (C) type, supplemented by humus layer (A) + parent material layer (C) type and humus layer (A) + parent material layer (C) + buried layer (Ab) type. ② Correlation analysis showed gully morphology was complicated by internal and external factors, and the single morphology was affected not only by internal and external factors, but also by its own morphology. ③ Redundancy analysis showed that the slope, soil configuration, and catchment area of the gully head were the main factors affecting gully head morphology, and were positively correlated with gully head morphology. The vegetation coverage of the gully head, the distance between crops and the gully head, the angle between the ridge and the gully head elevation were negatively correlated with gully head morphology. [Conclusion] The morphological characteristics of gully heads are complex, and the soil vertical difference is the fundamental internal factor. Gully head morphology is affected by both internal and external factors.