The laser characteristics at 2.94μm in YAG:Er3+ crystal were investigated. The internal cavity amplification, loss, threshold, directionality and output energy characteristics curve were measured. When the input was 288 J (T=28.5%), 2J/pulse energy was obtained (ηalops=1%,Pth=110J), when the output at transmittance T=0%,the laser threshold was 69J.