The high sensitivity terahertz detection module （HSTDM） is one of the scientific instruments of the China Sky Survey Telescope. HSTDM is a high-resolution spectrometer and the first space heterodyne receiver using niobium nitride （NbN）-based superconducting tunnel junction （Superconductor - Insulator - Superconductor （SIS）） mixer （the NbN SIS mixer）. The NbN SIS mixer must meet the specification requested for a space environment， such as high operation reliability， robustness to vibration， cosmic irradiation， and thermal variation. This paper presents the space qualification tests performed on the NbN SIS mixer， including sine and random vibration tests， single-particle irradiation test， total dose radiation test， and thermal cycling test. The mixer’s performance analysis confirms that it can meet the space application requirements of HSTDM.