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, this paper presents a systematic summary across three levels: material, chip, packaging and gate drive. This includes utilizing wide bandgap (WBG) materials, enhancing chip structure, adopting advanced packaging and improving gate drive design. The underlying principles behind these methods for increasing power density are summaried, and recent advancements are categorized and compared. The primary challenges in current research are highlighted, and the future development trend is forecasted.