Abstract: A hydraulic-drive system was developed and researched for solving the drive requirement of self-propelled sprayer.Firstly，hydraulic components of this drive system were one hydraulic piston pump，four hydraulic motors，parking brake，dividing-combining valve，etc.High and low speed switching and parking braking could be realized by adjusting oil supply pressure.Reverse pump and motors could achieve vehicle brake.A test was designed and carried out with full-load，maximum speed and high temperature.Results showed that theory of hydraulic-drive system was correct and every function could be achieved successfully.Maximum working pressure was 39 MPa，drain pressure was always under 0.3 MPa，and charge pressure was about 2.4 MPa.Meanwhile，flow rate of exchange valve to pump was between 11L/min to 14L/min.It was reasonable for cooling and washing.The temperature of hydraulic fluids in line could always be maintained below 70℃.In conclusion，hydraulic-drive system was reliable，and main parameters were all within the reasonable range.