A widely tunable long-infrared optical parametric oscillator (OPO) based on ZnGeP₂ (ZGP) with nanosecond pulses output in dual bands was reported in this paper. As a fundamental laser of ZGP-OPO, KTP- OPO of 2.1 μm based on type Ⅱ phase match was pumped by 1064 nm fundamental delivering <10 ns pulses at 50 Hz. Furthermore, the ZGP-OPO of 7-11 μm based on type Ⅰ phase match was designed. Continuous-tunable signal wavelengths of 2.815-2.963 μm corresponding idle wavelengths of 7.82-9.08 μm was obtained using angle tuning of ZGP. Continuous-tunable signal wavelengths of 2.624-2.662 μm and 2.745-2.956 μm, which correspond the idle wavelengths of 7.94-9.07 μm and 10.20-10.82 μm respectively , were obtained using pump wavelengths tuning. The single-pulse energy was 0.8 mJ at 8.03 μm, pump to idler conversion efficiency was 9.4%.