As a complicated distributed system, radar network system encounters various attacks. In order to study the impact of cyber attacks on the performance of radar network system, a kind of replay attack mode for radar network system is proposed. Firstly, a target motion model and a system model are established. Then, the influence of the replay attack on the position estimation error of the monostatic radar is analyzed. For the abovementioned reasons, the influence on the tacking performance of the radar network system is extended. Finally, the relationship between the attack parameter and the position estimation error is studied. The state estimation error of monostatic radar and radar network system under replay attack, as well as the relationship between singlestation radar and radar network estimation error and attack strength are obtained by simulation. The simulation results show that for monostatic radar, replay attacks can cause huge tracking errors, and the attack effect is directly proportional to the attack strength. When the target of replay attack is a radar network system, a reasonable selection of attack parameters is required to produce a significant attack effect.