As　a　novel　traffic　safety　facility,　the　decorated　sidewall　in　tunnels　plays　a　crucial　role　in　improving　the　safety　and　upgrading　the　driving　environment.　The　design　element　spacing,　frequency　patterns　and　color,　are　important　elements　in　the　design　of　the　tunnel　wall　decoration.　In　order　to　analyze　the　impact　of　the　tunnel　sidewall　decoration　element　complexity　on　the　driving　behavior　under　different　driving　conditions,　this　paper　performs　a　detailed　visual-action-cognitive　driving　task　design.　In　the　driving　simulation　test,　three　sidewall　decoration　schemes　for　different　element　complexities　(character,　character　and　ribbon,　ribbon　and　snowflake)　are　designed　at　the　level　of　pattern　frequency　and　spacing　respectively　fixed　at　1.26　Hz　and　17.5　m,　compared　with　the　tunnel　without　sidewall　decoration.　Therefore,　thirty　drivers　are　recruited.　Six　indexes,　including　the　acceleration　and　lateral　position,　are　considered　to　construct　the　evaluation　index　system　from　the　aspects　of　speed　adjustment,　operation　stability　and　attention　concentration　levels.　The　significance　and　effect　size　of　the　indexes　are　explored　using　the　ANOVA　two-way　repeated　measures.　The　fuzzy　comprehensive　evaluation　model　based　on　the　entropy　weight　method,　is　used　to　compare　the　effects　of　four　sidewall　decoration　schemes.　The　results　show　that　the　complexity　of　the　sidewall　decoration　elements　highly　affects　the　speed　adjustment　level,　operation　stability　level　and　attention　dispersion　level　of　the　drivers.　The　results　of　the　fuzzy　comprehensive　evaluation　show　that,　compared　with　the　four　sidewall　decoration　schemes　in　the　whole　and　middle　sections　of　the　tunnel,　the　design　scheme　with　the　mural　elements　as　characters　under　the　condition　of　fixed　frequency　and　spacing,　has　a　higher　comprehensive　score.　This　indicates　that　adding　appropriate　mural　elements　on　the　sidewall　of　the　tunnel　improves　the　longitudinal　driving　stability　and　speed　control　ability　of　the　driver,　and　makes　the　driving　experience　more　comfortable.　This　paper　demonstrates　that　a　reasonable　tunnel　sidewall　decoration　plays　a　crucial　role　in　improving　the　safety　of　the　tunnel　driving　environment.　Finally,　it　provides　a　theoretical　support　and　technical　guarantee　for　improving　the　traffic　safety　using　tunnel　sidewall　decoration.