1319 nm or 1338 nm laser can be generated by secondary transition of Nd3+ ion from 4F3/2-4I13/2 in YAG crystal. The stimulated emission cross sections of both spectral lines approach to each other, and are 1/5 of that of 1064 nm primary transition. In order to achieve laser of single spectral line in secondary transition with high efficiency, three-chromatic mirror technology is used to restrain spectral lines of primary transition and other transition in secondary transition,and then several lasers of single spectral line in secondary transition have developed: 1) LD pumped 1319 nm or 1338 nm TEMo, mode Nd:YAG CW laser. Output power 200 mW, efficiency 20%; 2) Kr lamp pumped 1319 nm TEM00, mode Nd:YAG CW laser. Output power 6 W, efficiency 0.12%; 3) Kr lamp pumped 1319 nm high power Nd:YAG CW laser. Output power 100 W, efficiency 1.67%