Focusing on the friction-type coupler rotation behavior under compressive forces, the relationship between the longitudinal distance of secondary lateral stoppers of heavy haul locomotives and the coupler rotation angle was analyzed. A train dynamic model, including two sets of eight–axle heavy haul locomotives, a dummy freight vehicle and four friction-type coupler and draft gear systems with hysteretic characteristics, was built to study the effect of the longitudinal distance of secondary lateral stoppers on the coupler compressive stability capacity and the running safety of trains under braking condition. Numerical results indicated that the longitudinal distance of secondary lateral stoppers had an important influence on the coupler compressive stability capacity and the running safety of trains. Under 500 kN coupler compressive forces, the maximum coupler rotation angle and carbody lateral displacement were respectively 10° and 60 mm, and the train safety index exceeded the safety limit value when the longitudinal distance of secondary lateral stoppers was set to 10 m. When the longitudinal distance of secondary lateral stoppers was increased to 14 m, the maximum coupler rotation angle and carbody lateral displacement were reduced by 70% and 67%, respectively. The train safety index was much smaller than the safety limit value. During the design stage of heavy haul locomotives, the longitudinal distance of secondary lateral stoppers should be appropriately increased in order to improve the running safety of trains under braking condition.