The wall spray coating task requires robot to handle a spray-head to cover the whole interior wall surface. In this paper a manipulator is used to complete such task where a Cartesian constraint path is firstly generated by breadth first search (BFS) based on the boustrophedon decomposition, and then the Cartesian path will be converted to joint sequences. In addition, corners formed by two walls as the non-differentiable area are analyzed and fitted by Bezier curve. Finally, a sphere cap constraint planner is proposed to deal with wall suspended with multiple aligned pipelines. A 6DOF KUKA robot arm was employed to do the spray coating task in a building, and the experiments will demonstrate the effectiveness and efficiency of the proposed approach.