The invention relates to a high-pressure gas-liquid separation control device and a control method thereof. The high-pressure gas-liquid separation control device comprises a horizontal or vertical separating tank and a PLC (programmable logic controller), wherein a liquid outlet and a gas outlet of the separating tank are connected with a float valve; the coaxial float valve communicates with a balance valve; the upper part of the coaxial float valve is connected with a gas discharge pipeline, and the bottom is connected with a liquid discharge pipeline; the liquid discharge pipeline and gas discharge pipeline are respectively provided with an electric control regulating valve and a flowmeter; the liquid outlet of the separating tank is provided with a liquid level stabilizer; the liquid inlet of the separating tank is provided with an electric control regulating valve; the separating tank is also provided with a rectifying plate and a magnetic turning plate liquidometer; the PLC respectively monitors the separator working pressure, gas flowmeter water content and liquid flowmeter race condition; and the PLC controls the electric control regulating valves at the liquid inlet, the liquid outlet and the gas outlet. The high-pressure gas-liquid separation control device and control method thereof solve the problem of liquid discharge at the gas outlet and gas discharge at the liquid outlet due to the insufficient separating capacity of the low-pressure separator and manual control of the high-pressure separator.