TCA residue in soil, wheat and corn plants in different periods was studied by field and pot experiment. Result obtained showed that TCA could be kept in the soil under field condition for seven months; the highest TCA content was detected in seedling (trifoliate) stage of the plant, TCA content decreased ripadly with the plant growing, and a very small amount of TCA was detected in seed. Discussion is made on the factors affecting absorption of TCA by crops and the relationship between TCA residue in soil and TCA content in plant.