Salt transfer law for cotton field with drip irrigation under the plastic mulch was analyzed from two aspects: different postemergences and different direction (vertical direction and horizontal direction). The results show that with the retardation of postemergences, the accumulation of salt in 0-50cm soil layers decrease in different extent. The accumulation of salt in vertical direction increase at the soil layers from 50 to 70cm, but the one at the soil layers from 70 to 90cm change a little. The accumulation of salt in horizontal direction at the narrow row is more than any other position and the one under the emitter is least.