Abstract: The insulation protection of cable harnesses is of significant importance for ensuring the safety of power supply and distribution in spacecraft. Based on the current status of secondary insulation protection in spacecraft cable harnesses, this study analyzes the causes of inadequate secondary insulation implementation using two specific types of spacecraft as examples. Three key contributing factors were identified, namely, inability to verify the implementation status of secondary insulation through image documentation, ambiguity in designated implementation areas for secondary insulation and unclear timing for implementation verification of secondary insulation. Corresponding optimized protection measures are proposed, effectively enhancing the insulation protection quality during spacecraft harnesses installation.