COMSOL finite element simulation software was used to study the effect of bird droppings with different morphological characteristics on sulator flashover. By studying the influences of the length and viscosity of bird droppings on the flashover and the process of insulator flashover caused by the bird droppings falling, the calculation method of the combined air gap breakdown voltage composed of multiple sections bird droppings with different viscosities was obtained. The results show that the higher the viscosity of bird droppings, the better the continuity of bird droppings, the lower the breakdown voltage of the air gap, which is easy to cause the composite insulator flashover. Therefore, in order to improve the protection ability of anti-bird shield to high viscosity long bird droppings. the anti-bird shield must have the ability to reduce the length of bird droppings. In this study, a deflector groove was designed on the surface of anti-bird shield, and the high viscosity long bird droppings can be divided into several sections of short bird droppings through the deflector groove. By reducing the length of bird droppings, the air gap length increases, so as to increase the breakdown voltage and decrease the probability of bird droppings flashover.