As one of the key components of high-power optically pumped THz laser, hybrid metal-mesh output coupler is critical for the output power and the beam quality. A model for the hybrid metal-mesh output coupler has been developed. The reflectance, transmittance and loss of the coupler was evaluated. Output couplers at 2.52 THz have been fabricated. The reflectance and transmittance are 70% and 11% for type I, 87% and 4% for type Ⅱ.The coupler can sustain high-power CO2 laser pump with the reflectivity over 95 %. This research provides theoretical and technical supports for developing high-power optically pumped THz laser.