The high stiffness is required when the parallel mechanism is used in the machine tool.As three pairs of active rods in the manipulator are crossed,which is different from the original Stewart mechanism,the length of each rod are average distributed.In order to verify the stiffness performance of this parallel mechanism,Lodrigues parameters were used to build the Jacobian,and the expression of stiffness was given.The minimum stiffness and single stiffness in several different direction were described,and the stiffness distributions throughout the entire task workplace were given.The characteristics and advantages are shown through the comparative analysis,and the results offer the evidence for the design as well as the use of this type of parallel mechanism.