The invention discloses a safety 
system with a closed-loop negative Poisson ratio structure, of an automobile and a design method. The 
automobile safety system comprises a closed-loop framework structure formed by mutually and sequentially connecting the head end and the 
tail end of a front bumper, the head end and the 
tail end of a left 
energy absorbing box, the head end and the 
tail end of a rear bumper and the head end and the tail end of a right 
energy absorbing box; the front bumper is a front bumper crossbeam with a negative Poisson ratio structure filling core; the rear bumper is a rear bumper crossbeam with a negative Poisson ration structure filling core; the left 
energy absorbing box is a left energy absorbing box longitudinal beam with a negative Poisson ratio structure filling core; and the right energy absorbing box is a right energy absorbing box longitudinal beam with a negative Poisson ratio structure filling core. The design method comprises the following steps of firstly, establishing a parametric model of the bumper crossbeams and the negative Poisson ratio structure filling cores, and establishing an approximation model by combining Latin 
hypercube and a response surface method, and multi-objective optimization design is performed by applying multi-objective optimization 
algorithm in accordance with 
crashworthiness and light weight properties. By adopting the 
closed loop design and using excellent 
energy absorption property of the negative Poisson ratio structure, the 
automobile safety system disclosed by the invention can improve the energy absorbing and buffering capacity of the structure in the collision process of an automobile, enhance the protection of the automobile to occupants and pedestrians, and reduce the damage of collision to an automobile body.