To accurately calculate the surface heat load for the design of the anti-icing system of an aircraft, the method for calculation of anti-icing heat load was studied and the calculation process was presented. And the influnce of the incoming flow speed, flight altitude, temperature, liquid water content and median volumetric diameter on the surface heat load distribution was studied. The results showed that: (1) the heat load was mainly located at the leading edge of the wing, and the closer to the tip of the wing, the larger the heat load value. The heat load curve had a trough in the middle and two shoulders at each side. (2) The non-zero range and the amplitude of the surface heat load were in proportion to the incoming flow speed and water median volumetric diameter. The variation of the flight altitude had trivial influence. As the incoming flow temperature decreased or liquid water content increased, the amplitude of the heat load increased, but the distribution range of the curve remained the same. The distribution range of the heat load on upper wing surface increased about 50% as the diameter of the water droplet increased 10 μm.