Power semiconductor modules are the core energy conversion units in power converters. By optimizing their design, the power density can be significantly enhanced. However, current design methods lack systematic summaries. To address this, a systematic summary across four levels(material, chip, packaging and drive) was presented. This included utilizing wide bandgap materials, enhancing chip structure, adopting advanced packaging and improving gate drive design. The underlying principles behind these methods for increasing power density were summarized, and classified and compared the existing research on improving the power density of converters based on power semiconductor module design. The primary challenges in current research were combed, and the future development trend was forecasted.