The invention provides a pressurization device and method for an associated gas compressor. The pressurization device comprises an inlet pipeline, a connection pipeline and an outlet pipeline. A gas-liquid separation device is connected between the inlet pipeline and the connection pipeline, and the associated gas compressor is connected between the connection pipeline and the outlet pipeline. Associated gas enters the gas-liquid separation device through the inlet pipeline, then enters the associated gas compressor through the connecting pipeline to be separated by a gas-liquid separator of the associated gas compressor and pressurized, and is pressed into the outlet pipeline through a check valve. According to the pressurization device and method for the associated gas compressor provided by the invention, the associated gas is subjected to two-time separation before entering compressor, specifically, the associated gas is subjected to deep gas-liquid separation through the gas-liquid separation device and then subjected to secondary separation through the gas-liquid separator of the associated gas compressor; due to two-time gas-liquid separation, liquid in the associated gas is reduced, and the separated associated gas is pressurized by the associated gas compressor. The liquid check valve is added to the outlet pipeline, so that the service life of easily damaged parts of the compressor is prolonged.