An in-line pulse tube cryocooler regenerator is designed. An experimental platform for in-line low temperature oscillatory flow pressure drop is established for the regenerator. Experimental study is carried out for the pressure drop and the change rule of pressure ratio at the cold end. The influences of input power, frequency, cooling temperature and initial pressure on the pressure drop of the regenerator are analyzed. The results show that the lower the operating frequency of the crycooler is, the lower the cooling temperature is and the greater the pressure drop of the regenerator is. The pressure drop under the initial pressure of 3.0 MPa is greater than that under the initial pressure of 3.2 MPa. The higher the pressure ratio at the cold end is, the higher the relative Carnot efficiency is. By increasing the pressure ratio at the cold end of the regenerator, the efficiency of the pulse cryocooler can be improved.