The invention discloses a liquid phase pressure difference sensor which comprises a shell. A support is arranged on the inner wall of the shell and connected with a rigid segregation board, the rigid segregation board is vertically arranged in the shell, one end of the rigid segregation board takes the support as a supporting point, the other end of the rigid segregation board can horizontally move, two sides of the rigid segregation board are respectively connected with one end of a telescopic pipe, the other ends of the two telescopic pipes are respectively fixedly connected with a fixing pipe, each fixing pipe penetrates the side face of the shell and is communicated with the outside, pervious materials are fixed into the fixing pipes, a sensing unit is arranged in a space formed by one telescopic pipe, the shell and the rigid segregation board, one end of the sensing unit is connected with the rigid segregation board, and the other end of the sensing unit is connected with the shell. The liquid phase pressure difference sensor fundamentally solves the problems that the sensing unit is easily corroded and interfered by detected media.