The invention discloses a tail gas purifying system for a vehicle. The system comprises a tail gas temporary storage tank, a tail gas filtering module, a tail gas purifying module, a tail gas discharging module and a circulating module; the tail gas temporary storage tank is connected with the tail gas filtering module; the tail gas filtering module is connected with the tail gas purifying module; the tail gas temporary storage tank comprises a discharging connecting port, a storage tank and a solenoid valve; the tail gas filtering module comprises an inner-layer filtering net, a quality detector, a connecting pipeline and a liquefying mechanism; the tail gas purifying module comprises an oxygen content detecting mechanism, an electrolysis mechanism, a harmful gas isolating mechanism and a liquid outlet pipe; and the circulating module comprises a circulating pipeline and a content detector which are mounted in the circulating module. With the tail gas purifying system for the vehicle, the tail gas filtering module and the tail gas purifying module are adopted, so that the tail gas is filtered and purified effectively, dust particles and harmful gases in the tail gas are greatly removed, the damage of the tail gas to human bodies is reduced, the pollution of the tail gas to the air is reduced, and the system is relatively convenient to use and mount.