Aiming at the significant influence of timing parameters (i. e. sampling period and delay) on the con-touring performance of networked CNC (Computer Numerical Control) systems due to the involved networks,thispaper sets up a networked CNC system model with delay based on the modified Z transformation,and constructs therelationship between timing parameters and the contouring performance index, with the corresponding influence lawsbeing also obtained. The results show that (1) both the delay and its jittering increase the contour errors of multi-axis processing; (2) the sampling period is the primary factor influencing the contouring performance; (3) themulti- axis control actuation asynchrony caused by delay leads to the degradation of contouring performance; and(4) more attention should be paid to the influence of timing parameters on the contouring performance of high-speed networked CNC systems.