To improve the applicability of the conflict delay model between left-turn vehicle and straight vehicle in the opposite direction at two-phase intersection, the conflict delay was studied on the basis of M3 distribution. M3 distribution of time headway for straight vehicle is more suitable than negative exponent distribution at signalized intersection. The queue delay of left-turn vehicle and the affect of the number of straight queue vehicles on conflict delay at the beginning of green were considered when M3 distribution was used in this paper. Then a new conflict delay model at two-phase intersection was put forward and it proved effective. The result shows that the conflict delay model improved closely meets with reality and it proved effective. It consummates the theory of existing conflict delay calculation and can provide the theoretical basis for setting up signal phases further.