Cadmium (Cd) is a highly toxic metal that damages human health and normal plant metabolism, and often results in reduced crop growth and yield. To explore the Cd migration characteristic in paddy soil and ditch sediment in a small watershed, present study was conducted in two different Cd polluted paddy areas in Hunan Province, China. The Cd contents of ditch sediment and paddy soil in the typical polluted watershed (Beishan Town, Changsha County, China) and non-polluted watershed (Jinjing Town, Changsha County, China) were determinate. The results showed that the total Cd content and available Cd content in the ditch sediment and paddy soil in Beishan ranged from 0.50 to 6.29 mg kg⁻¹ and 0.26–1.72 mg kg⁻¹, respectively. The total Cd content and available Cd content in the ditch sediment and paddy soil in Jinjing ranged from 0.30 to 2.13 mg kg⁻¹ and 0.05–0.44 mg kg⁻¹, respectively. The total Cd content and available Cd content in the ditch sediment and paddy soil in Beishan presented logarithm decreasing trend with the runoff direction. However, the total Cd content and available Cd content in the ditch sediment and paddy soil in Jinjing presented linear increase trends with the runoff direction.