完善相关法律法规，用英语怎么说？

答案：
improve relevant laws and regulations

例句：
中国将保持外资政策的连续性和稳定性，完善相关法律法规，为外商创造良好的投资环境。
China will maintain the continuity and stability of its FDI policy, improve relevant laws and regulations and create a sound investment climate for foreign businesses

optimize the related laws and regulations

To prefect relevant laws and regulations

二楼的不错~