The　assumption　that　drivers＇　cognitive　level　on　road　network　in　the　day-to-day　route　choice　process　is　unchanged　is　important　for　traffic　network　theory.　In　this　paper,　experimental　approach　is　used　to　verify　this　assumption.　Firstly,　drivers＇　day-to-day　route　choice　process　is　modeled　into　two　cases:　providing　complete　and　incomplete　information.　Secondly,　two　sets　of　experiments　corresponding　to　the　two　cases　are　conducted.　The　experimental　results　show　that　the　assumption　is　not　reasonable.　Drivers＇　cognitive　level　on　road　network　under　the　two　kinds　of　information　is　fluctuant.　The　average　cognitive　level　of　providing　incomplete　information　is　lower　than　that　of　complete　information,　and　the　fluctuation　of　drivers＇　cognitive　level　is　smaller.　©　Copyright.