Abstract: The time node of foliar barrier application is the key to the Cd reduction efficiency of rice seed. Taking Hechuan District (purple soil) and Qianjiang District (yellow soil) of Chongqing as examples, the effects of different growth stages of foliar barrier agent on Cd reduction efficiency of rice seed were studied, aiming to find the best growth stage of rice foliar barrier agent application in the main soil types of Chongqing. The results showed that in purple soil area, only at heading stage (T2), leaf surface barrier spraying could reduce the content of Cd in rice seeds (0.151 mg·kg^-1) below the food safety limit, and only at tillering stage (T1), tillering stage and heading stage (T3) showed the effect of increasing Cd in rice seeds. All treatment groups in yellow soil showed Cd reduction effect in rice seed, but it was difficult to guarantee the safety of rice seed (Cd content in rice was 0.210-0.245 mg·kg^-1). The Cd reduction effect of only spraying at tillering stage (T1) was better than that at heading stage (T2). Soil Fe content is the key to the Cd reduction efficiency of rice seed applied with leaf surface barrier at different growth stages, and the iron film on root surface can block the transfer of Cd to the inside of rice root and the abovemoid tissue. It is recommended to apply foliar barrier agent at heading stage in purple soil area and twice at tiller stage and heading stage in yellow soil area, but comprehensive control technology (VIP n) should be adopted to ensure the safety of rice seeds. In addition, rice roots and stems and leaves have a strong ability to accumulate Cd, so it is recommended to remove rice roots from the field after rice harvest to increase the output flux of heavy metals in farmland soil