In order to provide a scientific basis for regulating the growth and development of direct seeding cotton in heavy metal cadmium contaminated farmland, the effects of planting density on the accumulation, distribution and yield of dry matter and cadmium were studied under the condition of heavy metal cadmium contaminated farmland. The accumulation dynamics of cadmium accumulation and dry matter accumulation in cotton under different densities were in line with the logistic model. With the increase of planting density, the accumulation of cadmium, dry matter and its distribution ratio in reproductive organs showed a trend of increasing first and then decreasing, and all reached the maximum at D7.5. The initial period of rapid accumulation of cadmium was earlier than that of dry matter accumulation. The initial time of rapid accumulation in the two years was 10.99 d and 12.41 d earlier, and the end time of rapid accumulation was 3.72 d and 8.63 d earlier, respectively. Increasing planting density reduced the enrichment coefficient of cotton plant population. The change trend of seed cotton yield with the increase of planting density was consistent with the accumulation of cadmium and dry matter accumulation, and reached the maximum at D7.5. Moderate density increase increased seed cotton yield and population accumulation of heavy metal cadmium, and the recommended planting density of direct seeding cotton was 75,000 plants per hectare. Keywords: cotton; planting density; dry matter; cadmium; seed cotton yield