If the pressure sensor of screw down cylinder in acid rolling line is placed outside, problems can not be ignored because of the pressure loss in pipeline extension and time delay of data acquisition. Oriented to the data acquisition system of pressure sensor which is designed for the screw down cylinder in acid rolling line, the rolling state of the actual screw down cylinder is simulated to do the high pressure experimental research about external installation of pressure sensor on screw down cylinder. The experiments show that in terms of 5 m long pipeline extension, the result of the relatively maximum pressure loss value in straight pipeline is 0719% under about 25 MPa hydraulic pressure, and the value in curved pipeline of 3 bends and 5 m long extension is 0998%. Also, the value of time delay meet the requirements of error at the same time. According to the experimental data, the external placement strategy of the pressure sensor was put forward and the application verification was carried out. The results show that the method of placement meets the requirements of the production in adjustment onsite.