The effects on turbine blade surface pressure and aerodynamic loss distribution of coolant-air inject from each of three individual rows of coolant holes on the blade leadingedge, and the rear of the suction and the pressure surface were investigated in a linear cascade. The experimental results showed that the changes in the pressure and aerodynamic loss distribution were dependent primarily on the amount of coolant added and the location of injecting holes. The pressure surface injection did not change the pressure distribution as clearly as did the suction surface injection due mainly to the difference of mainstream pressure gradients and velocity. The air injection from suction surface led to the largest effect on the loss increase while the air injection from the pressure surface exerted the least influence.