The invention discloses a system for generating the power through the temperature difference of liquid, and a power generation method of the system. The system provided by the invention comprises at least one thermoelectric power generation unit, wherein each thermoelectric power generation unit comprises a first liquid pool; at least one first pressure tank; a second liquid pool; at least one second pressure tank; at least one first hydraulic piston which comprises a first piston rod; at least one second hydraulic piston which comprises a second piston rod; an air exchange mechanism which isconnected with the first pressure tank and the second pressure tank; and power generation equipment. The system can generate power through the temperature difference between the temperature of the liquid with the first temperature range in the first liquid pool and the temperature of the liquid with the second temperature range in the second liquid pool, and can provide a power generation system which can generate the sustainable power generation.