The mid infrared laser, represented by the CdSe crystal optical parametric Oscillator, has a wide range of applications in many fields such as biology, medical treatment and military. In this paper, the methods of growing CdSe single crystal include melt method, flux method and gas phase method, in which gas phase method is most common, and the HPVGF technology has been gradually adopted. The intrinsic CdSe crystal used as OPO device is applied to kinds of laser, and the output power is increasing. Doping of Cr2+ can effectively improve the pumping efficiency and realize continuous wavelength adjustment.