Abstract: With the improvement of electricity market rules, the power system operator permits new energy resources to gradually participate in the frequency control ancillary service market. The participation of new energy resources greatly enhance the frequency regulation performance and mutual support of different energy resources. However, some frequency regulation resources are usually equipped with insufficient cyber security protection measures due to economic considerations. Under this situation, hackers may exploit the vulnerability of susceptible cyber physical systems to disrupt the operation of frequency control ancillary service market. Therefore, we analyze frequency modulation market game equilibrium considering the attack-defense game. First, we analyze the cyber attack behaviors aiming at manipulating the bidding information of susceptible resources. Second, we analyze the attack model aiming at maximizing the profit of the complicity. Next, a frequency modulation market equilibrium model considering the master-slave Stackelberg game of both sides of attack and defense is designed. Finally, the frequency modulation market equilibrium results based on the Column-and-Constraint Generation (C&CG) algorithm are analyzed. Through case analysis of 30-unit frequency regulation markets, the average deviation of capacity revenue change from 113.89% under attack to 12.56% after defense, indicating that the defender can to a certain extent suppress the market equilibrium deviation caused by the attacker.