The experiment of laser cooling of molecules generally needs multiple lasers with narrow linewidth and passive-stabilized frequency. We propose to use Pound-Drever-Hall (PDH) technique to lock the cooling laser onto the diode laser stabilized by the saturated absorption spectroscopy of Rb atom through the transfer optical cavity. The linewidth and long term drift of the cooling laser frequency could be controlled. The Fabry-Parot (F-P) optical cavity is designed and made, and the optical stabilization system is set up, and the optical transfer cavity is locked onto the reference laser through PDH technique.