For the effectiveness evaluation problem of missile saturation attacking mode， a simulation method based on attack-defense countering sequence is proposed under “many-to-many” condition. Under the described models of attacking missile and anti-missile firepower unit， the target allocation rules and allocation models are established. The fire channel saturation degree is outlined for describing the attacking target intensive degree， considering factors such as intercepting window， target channel occupation and release. The attacking success probability sequence is calculated fast using predictive impact point method， the saturation ability is evaluated based on attack-defense aspects and finally the engineering simulation flow is outlined. The applicability of the method under different conditions is verified under typical scenario settings， and can be used to guide the construction of attack-defense confrontation system.