Wall climbing robot is widely studied and used in a lot of industries such as cleaning, nuclear industry, construction industry and fire department due to the character of working on vertical wall. It is adopted because it can work in the dangerous space instead of people. The paper mainly studies path planning of wall climbing robot. Firstly, the paper demonstrates path planning of wall climbing robot on the plane conditions using basic ant colony algorithm and improved ant colony algorithm. Secondly, the paper proposes the minimum gravity consumption algorithm to execute path planning on the vertical wall. At last, the paper makes path planning with the fusion of ant colony algorithm and the minimum gravity consumption algorithm. The simulation shows that the algorithms are effective.