This paper presents a coupled and directly self-adaptive underactuated (CDSA) grasp mode, which has hybrid functions: firstly coupled grasp and secondly directly self-adaptive grasp. A novel multi-pulley-belt finger mechanism with springs is designed based on CDSA grasp mode. Compared with traditional coupled underactuated fingers or directly self-adaptive underactuated fingers, the grasp process of the new finger is more humanoid and its stability is better. Force analysis and size optimization rules of the finger are given. A multi-fingered robotic hand, CDSA Hand, based on the CDSA finger is developed, whose control system adopts a digital signal processor (DSP) circuit module with a keyboard and communication interface. The CDSA Hand has 5 fingers, 6 DC motors, and 15 joint DOF, 9 of which are CDSA joint DOF. The appearance and actions of CDSA Hand imitate human hand, whose size is 1.5 times of human hand. CDSA Hand weighs 1.6 kg and can grasp objects up to 0.5 kg. Simulation and experimental results show that CDSA Hand is able to realize CDSA grasp mode effectively.