The invention discloses a bamboo leaf flavonoid cellulose adsorbent, a preparation method and application thereof. The preparation method includes: mixing ionic liquid with a nonpolar protic solvent, and soaking poplar bits at temperature of 100 DEG C for 3h; recycling solid substance obtained after soaking to obtain the bamboo leaf flavonoid cellulose adsorbent, wherein a mass ratio of the ionic liquid to the nonpolar protic solvent is 5:1. Results show that the adsorbent prepared by treating the poplar bits with the ionic liquid (chlorinated 1-allyl-3-methylimidazole) and the nonpolar protic solvent according to a proportion of 5:1 at 100 DEG C has good adsorption effect on a bamboo leaf flavonoid standard solution with pH=8. Under action of the adsorbent, adsorption rate can reach 76.96%, which is obviously higher than that under other conditions. The method is high in adsorption rate, and raw materials are recyclable, so that the adsorbent is free of pollution and has good environmental and social benefit.