The debate about whether the capacity of working memory (WM) varies with the complexity of memory items continues. This study employed novel experimental materials to investigate the role of complexity in WM capacity. Across seven experiments, we explored the relationship between complexity and WM capacity. The results indicated that the complexity of memory items significantly affects WM capacity. However, given the non-linear relationship between complexity and WM capacity, we propose that WM may not allocate resources directly to each individual item. Instead, it might integrate these items to some extent before storage.