A method was put forward to avoid obstacles for an eggplant harvesting robot manipulator in Cartesian space. The obstacles were supposed equivalently as cylindrical-rings, and then a three-dimensional planning path problem was simplified to a two-dimensional one, which improved the real-time control performance greatly. Transforming the obstacles from work-space to configuration-space could control the robot joints directly, which could avoid complex coordinate translation using Jacobian inverse matrix. Moreover, processing properly image matrix mapped from C space could avoid the path planning failure under A star algorithm. The experimental results show that this algorithm with less computational amount and excellent real-time performance is suitable for harvesting natural growing eggplant automatically.