Numerical modeling has been given to describe the relation between optimal crystal length and the transmission of 946 nm output. The equation had been derived of the laser rate formula of the steady-state case in the laser cavity. By comparison of the output transmission between 946 nm and 1064 nm, we give a series of diagrams which discribe the minimized claims to coat in many cases. How the concerned factors influence the 946 nm lasing threshold and its output power has also been given. All the results will be useful for more efficient operation at 946 nm of Nd:YAG. The metholds adopted to deal with the low gain and quasi-three-lever or three-lever system will be enlightening.