The experimental results of high-repetition-rate and high-efficiency 2 μm laser is demonstrated on intracavity optical parametric oscillator (OPO) in KTP pumped by 1064 nm laser. The pumping threshold of KTP doubly resonant OPO is calculated, and the design method of intracavity KTP OPO is proposed. Walk-off compensation is realized by a pair of identical KTP crystals. When cut at φ=0°,θ=53°, a KTP OPO could get output at near degeneration wavelength of 2.128 μm. The average output power of 46.5 W at 2.128 μm is obtained under the condition of 470 W laser diode pump power at 808 nm and the acoustic-optical Q-switching repetition rate of 7.5 kHz. The optical-optical efficiency is 9.89% , the slope efficiency is 14.5% and the M2 of the output beam is less than 2.8.