A high-repetition-rate high-efficiency 2 μm laser was demonstrated. The tuning curve of the type Ⅱ phase matching KTP crystal pumped by 1.064 μm laser was calculated and it shows that when cut at φ=0°, θ=54°, a KTP optical parametric oscillator (OPO) gets output at near degenerated wavelength at 2 μm. The pump source was 1.064 μm Nd∶YAG module. Walk-off compensation was realized by two short crystals in intracavity doubly resonant optical parametric oscillator (DROPO) and the average power of 23.6 W at 2.12 μm is obtained. The pulse repetition frequency of acoustic-optic Q-switch was 7 kHz and the slope efficiency of 808 nm laser diode (LD) to 2 μm laser was higher than 19%.