To implement reliable locking under launching mechanical environment and low-impact and fast-response unlocking on-orbit for the CubeSat “Star of Aoxiang”, a non-pyrotechnic door release mechanism was proposed which locked by reset spring at the time of power off and unlocked by electromagnetic force at the time of power on. Firstly, according to the system requirements, the work principle of electromagnet door release mechanism was introduced, and the coupling dynamical models involving mechanical-electrical-magnetic characteristics were established. Secondly, the multi-constrain and multi-objective problems of electromagnet parameters were solved based on the ground tests, after that, the simulation verification of the optimized parameters was implemented. Then, the functional tests for a prototype of the electromagnet door release mechanism were carried out. The measurement values agreed well with the simulations results, which showed that the unlocking time was 41.2 ms and the current was 2.2 A and the energy consumption was only 2.5 J at the typical voltage of 28 V. Finally, on the condition of mechanical and thermal-vacuum ground environment and down-deflection of ±5 V, the electromagnet door release mechanism could lock and unlock reliably. The proposed door release mechanism has successfully applied to unlocking and launching the CubeSat “Star of Aoxiang” on-orbit. It provides reference for further standardization design of door release mechanism for following CubeSats and other micro-satellites.