Here, in order to study longitudinal response of cable-stayed bridge under braking state of random traffic flow and vibration control effect of viscous damper, firstly, combining the collected traffic load data and the key parameters statistics of traffic flow, random traffic flow models with 3 kinds of traffic flow density were established.Secondly, based on the vehicle-bridge system coupled relation, the improved half search method was used to determine the vehicle loading method of single girder model, and the vehicle-bridge coupled analysis module of the single girder model was compiled.Finally, longitudinal response of a cable-stayed bridge under braking condition, vibration control effect of longitudinal viscous damper and braking influencing factors were analyzed using the established random traffic flow braking model.The results showed that under braking state of random traffic flow, the braking response in opposite direction can be produced, and the bridge structure response is larger than that under normal random traffic flow; longitudinal viscous damper can effectively control the bridge’s longitudinal displacement, the smaller the speed index α, the larger the damping coefficient C and the more prominent the control effect, the maximum control efficiency can reach about 90%; the braking response and braking coefficient of the bridge’s second half are obviously larger than those of the first half; the more the braking lanes, the larger the braking response and braking coefficient; for the traffic flow density, the law of the braking response and braking coefficient is: dense flow > moderate flow > sparse flow.