The invention discloses a multi-module parallel-connection oil balancing system which comprises more than two modules, an oil balancing pipe and an air suction main pipe. Each module comprises more than one high-pressure cavity compressor, oil separators arranged on the high-pressure cavity compressor and air-liquid separators arranged on the high-pressure cavity compressor, air outlets of the oil separators are connected with an outdoor heat exchanger or the air suction main pipe, and oil balancing ports of the oil separators are connected with the oil balancing pipe; an air suction port of each compressor is connected with an outlet of the air-liquid separator of the compressor, and the air suction port of the compressor is further connected with an oil retuning port of the oil separator of the compressor through an oil returning capillary pipe; an inlet of the air-liquid separator of each compressor is communicated with the air suction main pipe; a decompression valve is further connected between the air-liquid separator of each compressor and the oil balancing pipe, and an opening pressure value of the decompression valve is preset. The invention further relates to a control method. According to the multi-module parallel-connection oil balancing system and the control method, the oil balancing pipe is effectively prevented from bursting, and reliable operation of a unit is guaranteed.