Rear-end crash is one of the important types of road traffic accidents with the characteristics of heavy casualties.Among the accidents,it has caused greater casualties and higher mortality in the passenger car crash into truck accidents.According to the analysis of lots of traffic accidents,its found that the truck rear under-run protection device has good protective effect and can reduce casualties in this kind of accidents.Only the analysis based on actual accidents data is able to provide real foundation for improving the rear under-run protection device.So this paper will,on the basis of actual accidents data,study on the determination method of the target value of prevention of truck rear under-run protection device.In order to carry out research on the basis of actual traffic accidents data,a large number of traffic accident cases has been collected and in-depth accident investigation has been conducted.In order to study a method on the target value of prevention of truck rear under-run protection device,some accidents has been appropriately chosen as data samples of road traffic accidents.The cumulative probability distribution was introduced into the study.Through analysis and deduction,the cumulative probability function of impact force has been established,and the characteristic point matrix of impact force has been determined,and the determination method of the target value of prevention has been finally found out.The function concluded by this method will introduce the weight of truck and the target probability of prevention so as to obtain the target value of prevention.The method can provide support for the optimization of rear under-run protection device.This paper further focuses on method exploration of the automotive safety technology as well as the vehicle standard key parameters on the basis of actual traffic accidents data,so it can also provide reference for other key parameters to be studied.