With the rapid development of quantum cryptography, infrared single-photon detection becomes the key technology in this research field. A high-speed InGaAs/InP avalanche photodiode (APD) is presented based on single-photon detector with a 1.25 GHz gating frequency, using the technique of sine wave gating and filtering. When the detection efficiency is 10.3%, dark count probability per gate is 1.3×10-6 and the afterpulse probability per nanosecond is 5.6×10-5. This kind of detector can significantly enhance the performance of quantum cryptosystem in terms of secret key rate and transmission distance, which paves the way towards the practical applications of the next generation quantum cryptography.