NOVELTY - Large-scale microalgae harvesting specific device comprises a high position microalgae culturing solution reservoir equipped with filter cloth and is located on the plate-and-frame filter press. The discharge port of microalgae culturing solution reservoir is connected with feeding port of plate-and-frame filter press via connecting pipe I. The connecting pipe I is provided with a pressure pump. The pore size of filter cloth is 0.5-5 mu m.    USE - The specific device/method is used in producing oils and fats, and bio-diesel (claimed).    ADVANTAGE - The method consumes less energy, is short, and has good dehydration effect; does not require secondary modification for the industrial equipment; can be used repeatedly; and avoids the loss of equipment and materials.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for microalgae harvesting using the device, comprising (i) opening the discharge port of the microalgae culture solution reservoir, passing the to be separated micro-algae culture in microalgae culture solution reservoir through a filter cloth, which is clamped because of gravitational potential energy, introducing into the plate-and-frame filter press by the connecting pipe I, (ii) opening the plate-and-frame filter press connected with the connecting pipeline II, and flowing out the culture medium supernatant liquid automatically, (iii) slowing or stopping the liquid flow speed of culture medium flowing from the connecting pipeline II, opening set upper part of the pressure pump connected with the connecting pipeline I, controlling the pressure at 0.05-0.12 MPa, passing the residual micro-algae culture liquid from reservoir through connecting pipe I into hydraulic plate-and-frame filter press machine, and flowing the culture medium supernatant liquid from connecting pipeline II, (iv) maintaining the pressure in pressure pump at 0.05-0.12 MPa until there is no liquid flow via connecting pipeline II, blowing the residual liquid in the plate-and-frame filter press, and (v) closing the pressure pump, opening the plate-and-frame filter press, separating the filter cloth, filtering the obtained micro-algae to form algae mud cake automatically fall into the plate-and-frame filter press, then into the lower part of the micro-algae collecting plate to obtain micro-algae in large scale.