in this paper, a new type of lightweight passive deployment mechanism based on the tape spring and the shape memory alloy is presented for the secondary mirror of a deployable space telescope. in this passive deployment mechanism for the secondary mirror, the high elastic potential energy of the folded tape springs is used as driving force when the support structure is extended, and the high stiffness characteristics of the circular arc cross section of the tape spring can be used to achieve structure self-locking after deployment. then a deployable space telescope combined with lightweight passive deployable mechanism for the secondary mirror is designed for applying to nanosatellite imaging. furthermore, a lock-release device is designed to achieve the function of locking the folded structure and releasing on orbit by taking advantage of the phase transformation characteristics of shape memory alloy with temperature changing. finally, the correction method for the deployment error of secondary mirror is discussed. the temperature of the tape springs is controlled respectively to make a required length change. this can achieve the purpose of adjusting the position of the secondary mirror and improve the deployment accuracy.