Because of the unique quantum effect, quantum dots(QDs) have attracted wide attention in various fields for many years. In order to study the nonlinear optical properties of ternary Cd_xPb_1-xSe QDs, a convenient synthesis method of high-quality QDs was developed, on the basis of which the nonlinear optical properties of the QDs were studied using Z-scan technique under 532 nm laser radiation. The results indicate that the high-quality Cd_xPb_1-xSe QDs with uniform size and highly crystalline nature are successfully achieved by a improved "one-pot" synthesis method with the synthesized N-oleoylmorpholine used as solvent, and that the nonlinear absorption coefficient and nonlinear refractive index of Cd_0.5Pb_0.5Se were 1.01×10^-9 m/W and -1.1×10^-10 esu, respectively, showing much more remarkable optical nonlinearity compared with binary CdSe QDs. Thus, the ternary Cd_xPb_1-xSe QDs should be of potential in laser protection and photoelectric switch, etc.