The invention discloses a turbine blade gas metal arc welding water erosion preventing method. The method comprises the following steps that firstly, a blade is fixed to a cold metal transition welding device through a clamp; secondly, according to the blade type and the groove type, the position of a welding gun is adjusted, and parameters are set; thirdly, surfacing is carried out on a fusion covering groove, protective gas is supplied, and the fusion covering groove is stacked through multiple times of lap joint, a surfacing welding stick is a Stellite 6 solid wire, the diameter of the welding stick is 1.2 mm, and the protective gas is the mixed gas of 98% of argon and 2% of carbon dioxide; and fourthly, the blade is dismounted, and the water erosion preventing treatment is finished. According to the turbine blade gas metal arc welding water erosion preventing method, the combination of surfacing materials and base metal alloy can be achieved, the water erosion preventing capability is equivalent to the water erosion preventing capability of a laser cladding water erosion preventing method, but the technology cost is greatly reduced, and large-scale application and popularization are facilitated.