Rape (Brassica campestris L.) is frequently planted in oasis soils from the Northwest arid areas, and Cd, Pb, Zn, Ni are the common pollutants, which are widely distributed in soil environment. By pot experiments to simulate Cd-Pb-Zn-Ni combined pollution, and using Tessier sequential extraction, this paper studied the effect of Cd-Pb-Zn-Ni combined pollution on the growth of rape, the transformation and tendency of chemical forms of heavy metals in soils, and bioavailability to the rape. Dry weight, root height and the concentration of Cd, Pb, Zn and Ni in different parts of rape was measured after one growing season(66 days). As Cd-Pb-Zn-Ni combined stress levels rising, the dry weight of rape first increased and then decreased, the growth of root was first promoted and then inhibited. The chemical speciation of heavy metals contains exchangeable form, carbonate bound form, ferric-manganese oxide form, organic matter form and residual form. Cd, Pb, Zn and Ni mainly existed in residual form, while the concentrations of exchangeable form of them were all low in soils for control. With the increasing concentration of exogenous heavy metals, the concentration of various forms of Cd, Pb, Zn and Ni increased in soils. And the fractionation character of heavy metals transformed greatly. The exchangeable form of Cd, Pb, Zn and the carbonate bound form of Ni had the greatest response when the exogenous Cd, Pb, Zn and Ni were added jointly, where rape were planted according to the coefficient of variation(Cv). Meanwhile,the activeness of Cd, Pb, Zn and Ni enhanced considerably according to mobility factor. Furthermore, the main chemical speciation of Cd and Pb changed from residual form into carbonate bound form and ferric-manganese oxide form rapidly, while the main chemical speciation of Zn changed from residual form and carbonate bound form into carbonate form and ferric-manganese oxide, and the main chemical speciation of Ni changed from residual form into carbonate bound form. The concentration of Cd and Zn in stems and leaves were higher than which in root, while the concentration of Pb、Ni was converse. More Cd and Zn can be conveyed to the stems and leaves by rape, however, Pb and Ni are mainly accumulated in roots synchronously according to the ratio of the concentration of heavy metals in stems and leaves to the concentration of heavy metals in root. Correlation analysis and the stepwise linear regression equation was made between the concentration of Cd, Pb, Zn and Ni in different parts of rape and the concentration of various forms of Cd, Pb, Zn and Ni in soils to explore which chemical speciation could be mainly accumulated by rape. The main contribution form of uptake of Cd and Zn by all parts of rape was exchangeable form, the main contribution form of uptake of Cd by root transformed from exchangeable form to organic matter form, the contribution form of uptake of Pb by root and Ni by various parts of rape were carbonate bound form.