A soft actuator module (SAM) actuated by shape memory alloy (SMA) springs was proposed in this paper. The SAM can realize a three-dimensional bending movement. Taking the SAM as module unit, a four-joint soft manipulator was modularly assembled. Based on the characteristics of SMA resistance, a self - feedback control system was established, and the parametric analysis of the SAM was carried out. Furthermore, a multi-model locomotive control system of the soft manipulator was built to grasp objects by curling its arm, which proves the flexibility in spatial motion of the soft manipulator.