The parper deals with the influence of changes of cropping system from upland farming to rotation of rice and upland farming on the total content, form and availability of zinc in Shajiang black soils studied by using the sequential-extraction method in combining with the mathematical analysis methods of principal component analysis and linear regression. The residual, crystalline iron oxide-bound, amorphousiron oxide-bound, organically bound and exchangeable Zn of soils accounted for 75.60%-78.13%, 16.47%-20.00%, 2.19%-3.27%, 0.82%-2.86% and 0.56%-0.97% of the total Zn, respectively. These forms could be divided into three groups.The first group was exchangeable Zn, which the available Zn mainly came from,being the intensity factor of available Zn in soils. Organically bound Zn, amorphousiron oxide-bound Zn and crystalline iron oxide-bound Zn belonged to the second group which was the capacity factor of available Zn, in soils.The third group was the residual Zn, which was unavailable to plants but could be activated under artificial cultivation.Under the rotation of rice and upland crops, the ratios of exchangeable Zn and crystalline iron oxide-bound Zn to total Zn decreased, but those of organically bound Zn and amorphous iron oxide-bound Zn to total Zn increased, which enabled Zn in soils to be activated and be more movable, and thus reduced the contents of total Zn and available Zn in cultivated layer of soils.