This article aims to meet the design requirements of the Guangdong Provincial College Students" Engineering Practice and Innovation Ability Competition for inertial cars. Based on the basic knowledge of theoretical mechanics, mechanical principles, and mechanical design, a small car with unpowered inertial drive for straight-line travel is designed. Through Solidworks modeling and simulation, and comparison of small cars based on different parameters, it was found that the structure design of the car is simple, the performance is good, it meets the requirements of the competition, and can achieve long-distance sliding.