In this study, the highest photon conversion efficiency of the first Stokes laser is 82.4%, which is also the highest conversion efficiency of deuterium gas stimulated Raman scattering pumped by Nd∶YAG 1064 nm wavelength in free space. The phenomenon of Raman gain hole-burning is discovered and explained. Appropriately increasing the gas pressure of Raman medium is conducive for inhibiting Raman gain hole-burning, which is useful in maintaining pump laser high conversion efficiency at the stimulated Raman wavelength shifting of large pulse energy laser. To further improve the pulse energy of the Raman laser, we reduce the pressure of the Raman medium and increase the waist size of the pump laser beam to achieve maximum single pulse energy of 245 mJ. Additionally, we employ LBO crystal to obtain the second-harmonic generation with an output wavelength of 780 nm, maximum energy of 57.3 mJ, and conversion efficiency of 36.1%. The measurement of beam quality confirms that the gas thermal effect degrades the Raman laser beam quality, which reduces the laser energy conversion efficiency of frequency doubling. Raman medium circulating or cooling technology is a method for increasing the pulse energy of the laser.