Abstract: For planar hinge four-bar closed kinematic chain the following is done:①several exact mathematic and verbal expressions of revolving pair condition are enumerated;②existence condition and location of revolving pair in the chain are studied. The conclusions can be used to determine the type of each hinge pair in the chain rapidly and accurately;③classification of the chain is made according to revolving Pair condition, From this classification,all types of planar hinge four-bar linkage are found out.