In the current judicial reform, compulsory designated defense system has been an important way to realize the full coverage of lawyers’ defense, but there are still many theoretical and practical problems. The fundamental purpose of the compulsory designated defense system and the compulsory defense system is to ensure that the accused obtains a lawyer’s defense. The extraterritorial compulsory defense system has relatively mature experience in the scope of application, initiation method, application stage, defense autonomy and legal remedies. For our country, the compulsory defense system has enlightening significance for improving the compulsory designated defense system. Specifically, it includes expanding the scope of application of the mandatory designated defense system focusing on sentencing standards, litigation process and litigation stage, clarifying legal consequences of violating the mandatory designated defense system in evidence qualifications and procedural validity, establishing a legal aid defense lawyer selection system, and improving the quality assurance system for mandatory designated defense.