Any motion of robotic manipulator will disturb its base in space due to the dynamic coupling. Such a disturbance will produce the serious impact between the manipulator hand and the object. Moreover, the disturbance will affect the communication with the ground and power supply for the space robot. On the other hand, compensating the disturbance using the attitude control system will consume large fuel which is limit in space. Therefore, a novel approach based on genetic algorithms (GA) is developed to find a global optimal path of a space robotic manipulator in joint space in order to minimize the disturbance to the base of space robot. The planning procedure is performed with respect to all constraints, such as joint angle constraints, joint velocity constraints, joint angular acceleration and torque constraints, and so on. We use GA to search the optimal joint inter-knot parameters in order to realize the minimum disturbance. These joint inter-knot parameters mainly include joint angle and joint angular velocities. We use an illustrative example to verify that GA-based optimal path planning method has satisfactory performance and real significance in engineering.