Cd_xZn_1–xS nanoparticles were obtained by sonochemical method and were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Ultraviolet-Visible (UV-vis), Fourier-transform infrared Spectroscopy (FTIR). Band gap of Cd_xZn_1–xS nanoparticles were determined in the range of 2.1 eV to 3.4 eV. Lattice structure of nanoparticles are changes from cubic to hexagonal by increasing of x value. At the formation process using three different capping agents (Polyvinyl alcohol (PVA),3-mercaptopropionic acid (MPA) and Styrene). From XRD results, the average sizes of Cd_0.4Zn_0.6S/PVA,Cd_0.4Zn_0.6S/Styrene and Cd_0.4Zn_0.6S/MPA nanoparticles were determined as 7 nm, 9 nm, and 5 nm, respectively. From SEM results, sizes of Cd_0.4Zn_0.6S/MPA and Cd_0.4Zn_0.6S/PVA nanoparticles are 10–15 nm and 4–5 nm. From EDX result, the elements ratio in finally formed sample overlaps with the initial ratios. The shift of the absorption band to the low frequency is due to the particle formation in the stabilizer, reduction of energy and the weakening of the vibration movement.