This paper describes a household service robot with two lightweight arms and a trinocular vision sensor. According to DH convention, the coordinate system of two arms is established, and position and orientation of the hand is computed. The inverse kinematics of the arm is solved with geometric and algebraic solution methods. By the trinocular vision sensor, robot can recognize the bottle and get its 3-D space coordinate. Through experiments, both correctness of the algorithm and stability of the robot control system are validated.