The all-solid-state green laser with KTP intracavity frequency doubling has been widely used in industrial processin g,military,medical field,laser display and precision measurement.But high power noise has been a major problem that plagues researchers for a long time.A low-power- noise all-solid-state green laser with KTP intracavity frequency doubling is reported for reducing gre en power noise in this paper.When controlling KTP to specific temperature at 19.8℃,with 300W injected electric power,we get 2.5W continuous green output and the power instability is less than 0.9% (10min).Co mpared with the worst case, it increases by about 70%,significantly improving the stability of the green las er output.Based on the fundamental longi tudinal mode polarization state and the Jones matrix,the influence of the phase delay of KTP on the resonator longitudinal mode oscillation is analyzed.The phase delay can be changed by controlling the temperature or the length of the KTP.By this method,the fundamental polarizatio n mode coupling is effectively curbed,resulting in a stable green output.This provides a new way to obtain a low noise all-solid-state green laser with KTP intracavity frequency doubling with a broad application prospect.