The water purification ability of 12 plants commonly used on floating island are compared, and factors that influence the ability are summarized. The results reveal that red leave beet (Beta vulgaris var cicla) has the highest total nitrogen removal rate amounting to 85.72%, while water spinach (Ipomoea aquatica) keeps the highest total phosphorus removal rate of 95.6%, and water spinach (Ipomoea aquatica) and Canna (Canna indica) both are able to remove nearly all the ammonia nitrogen  in the water. Moreover, the water body and the season should be considered when selecting plants on the floating bed, and a 30% floating bed coverage could help achieve the best effect. The results could provide theoretical basis for applying biological floating island to water ecological restoration.