A 3.8 μm periodically poled LiNbO₃ optical parametric oscillator based on high repetition frequency pumping is studied. The Nd:YVO₄ acousto-optic Q-switched laser is used, obtaining a fundamental 1064 nm laser with good beam quality, the repetition frequency at 25-35 kHz, the maximum average power of 6.1 W and the pulse width of 59.1 ns. The temperature tuning characteristic of MgO:PPLN crystal with the period Λ=29.5 μm under the 1064 nm laser pumping is simulated. Through experiments, the 3599.6-3845.5 nmmid-infrared laser is obtained at a temperature of 25-200 ℃. When the temperature of the PPLN crystal is 30 ℃and the pump power is 6.1 W, the mid-infrared laser is obtained with the maximum output power of 0.45 W and the repetition frequency of 35 kHz at 3845.5 nm.