In this study, we describe a passively Q-switched Nd∶YAG nanosecond laser capable of operating stably over 100 ℃ and at low temperatures. The resonator is based on a stable, double-Porro-prism cavity structure. A Nd∶YAG slab is side-pumped via a vertical-cavity, surface-emitting laser array, and the temperature is controlled by a thermoelectric cooler. The passively Q-switched crystal is Cr4+∶YAG. We have tested the performance of the laser at different temperatures with a 1 kW peak pump power and 1 Hz repetition frequency. The results show that the average output energy of the laser is 18.79 mJ, the standard deviation is 2.29 mJ, the pulse width is ~4 ns, the near-field spot diameter is ~5 mm, and the far-field divergence angle is less than 0.9 mrad in the temperature range of －75-40 ℃. The lasers has a small size, compact structure, and high reliability. It is thus suitable for space-laser applications under a wide range of low-temperature conditions.