A new integrated child safety seat is presented in this paper. The seat is a two-mode seat for a motor vehicle cooperable with an adult seat belt assembly to provide two modes operation including an adult seat mode and a child seat mode. The seat locates in the center of the rear seat. The structure of the seat was designed in detail. The height of the booster of the seat can be adjusted continuously according to the seated shoulder height of the child passenger. The depth of booster cushion also can be changed according to the size of the passenger. The sled test with the seat was conducted. The seat simulation models with different booster heights were developed using MADYMO software and validated. Then, these models were used to study the performance of the seat in frontal impact. Some key parameters of the seat were studied in simulation test. The results of the test and simulation show that the seat can provide effective protection for the children aged from 3 to 10 years in frontal impact.