Aiming at the problem of evaluating the operational effectiveness of tear gas in handling large-scale mass incidents, a operational effectiveness evaluation model of tear gas based on the improved ADC is proposed. The evaluation index system for the combat effectiveness of tear gas is established. For the Availability (A), Dependability (D), and Capability (C) in the model, combined with the actual usage of tear gas, analysis and calculation are carried out. The constructed model is utilized to evaluate the combat effectiveness of a certain type of tear gas in handling large-scale mass incidents. The evaluation results verify the effectiveness of this model.