根据文档:

对于在 `QStyle::SH_ComboBox_Popup 如 Mac 风格或 Gtk+ 风格.

The property maxVisibleItems is ignored for non-editable comboboxes in styles that returns true for `QStyle::SH_ComboBox_Popup such as the Mac style or the Gtk+ Style.

并且您可以使用样式表覆盖 SH_ComboBox_Popup 样式提示:

And you can override that SH_ComboBox_Popup style hint with a style sheet:

combo.setStyleSheet("QComboBox { combobox-popup: 0; }");