Abstract: A high pressure falling cylinder viscosimeter was developed, this unit can be used for determing the pressure-viscosity and pressure-density characteristics of lubricants. The viscous moving seal manner and rheologic flat-spacer sedentary seal structure was adopted in this apparatus. The highest work pressure reaches 1200MPa and it keeps the pressure over 48 hours at 1000 MPa without leakage. The results shown that the design of this apparatus is reasonable, it is of high accuracy in making and assembling, the mechanical strength of the bearing part such as the high-pressure cylinder is higher, the high-pressure parts have the good sedentary seal property and this apparatus can operate with stable pressure for a long time. The measured data shown that the pressure-viscosity test method has the advantages of good repeatability, high sensityvity and strong comparativity.