The invention provides a hydraulic control system for a lifting oil cylinder of an under-pressure operation machine. The hydraulic control system comprises a main reversing valve, a descending brake valve, an ascending brake differential valve, the lifting oil cylinder, a pilot handle, a remote pressure regulating valve, a differential selection valve and a pressure reducing valve. A hydraulic oiltank is connected with a hydraulic pump, the hydraulic pump is connected with the main reversing valve and the pressure reducing valve, the pressure reducing valve is connected with the pilot handleand the differential selection valve, the pilot handle is connected with the main reversing valve, the main reversing valve is connected with the descending brake valve and the ascending brake differential valve, the descending brake valve and the ascending brake differential valve are both connected with the lifting oil cylinder, the main reversing valve and the ascending brake differential valveare both connected with the hydraulic oil tank, the differential selection valve is connected with the ascending brake differential valve, and the remote pressure regulating valve is connected with the main reversing valve. The hydraulic control system for the lifting oil cylinder of the under-pressure operation machine is low in manufacturing cost and short in cargo period, has multiple functions of reversing, braking, differential motion, pressure regulation and the like, is low in maintenance and repair cost, and can be suitable for various complex well conditions.