The ethical and legal issues of autonomous vehicles caused by the rapid development of artificial intelligence have been discussed for a long time. The work aims to discuss the design strategies that car enterprises need to propose to meet the needs of various stakeholders as the L3 autonomous vehicles will be put on the market soon. This paper first sorts out the ethical and legal issues faced by current autonomous vehicles, then clarifies the ethical and legal relationship of L0-L5 autonomous vehicles based on the current technical conditions of autonomous driving and the practical activities of vehicle enterprises, and finally proposes design strategies of L3 autonomous vehicles. The design strategy to solve the ethical issue of autonomous driving is as follows. The L0-L2 autonomous driving has no ethical issues. L3 autonomous driving adopts the design strategy of transferring decision-making power, L4 autonomous driving adopts the design strategy of limiting operating conditions. Currently, L5 autonomous driving cannot be realized, and feasible design strategies for L5 autonomous driving ethical issues need to be further studied. The design strategy to solve the legal issue of autonomous driving is as follows. The legal liability subject of L0-L2 is human, and the legal liability subject of L4 and L5 is vehicle manufacturers. For L3 autonomous driving, there is a switching of control power or decision-making power in the process of man-machine driving, so the legal liability subject should be analyzed and judged according to the specific situation. Finally, the paper puts forward the judgment method and the design strategy for L3 autonomous driving legal liability.