Oil storage tank breather valve VOCs zero-emission device and using method thereof

The invention discloses an oil storage tank breather valve VOCs zero-emission device. The device comprises an oil storage tank, a breather valve, a breather valve cover cylinder, a soft bag, a compressor, a condenser, a water cooling machine, a storage tank, an oil pump and a stop valve, wherein the breather valve cover cylinder is arranged outside the breather valve and connected with the soft bag, the soft bag is connected with the compressor, the compressor is connected with the condenser, the condenser is connected with the storage tank, and the storage tank is connected with the soft bagand the oil storage tank separately. When pressure of the storage tank rises, the breather valve is opened, VOCs enter the soft bag, when pressure of the soft bag is larger than a set value, the compressor is started, and the VOCs enter the condenser to be condensed into liquid to enter the storage tank to be stored; and when pressure of the oil storage tank is low, the VOCs in the soft bag are sucked back into the oil st