Recently, luminescent organic crystals have been widely studied as new optoelectronic materials. However, corrosion and dissolution of organic crystals by solvents have always been a great challenge for the application of organic crystals in various fields. In this work, we propose a general method of fabricating a solvent-resistant coating to prevent organic crystals from being corroded or dissolved by organic solvents. The coatings involved layer-by-layer assembly of poly(diallyldimethylammonium) (PDDA) and poly(styrenesulfonate) (PSS) onto crystals, followed by immersing the coated crystals into polyvinyl alcohol (PVA) aqueous solutions for 2 minutes. The coated crystals can remain intact over 24 h in common organic solvents without being damaged and even insoluble in dichloromethane for 5 days. Moreover, the thin and transparent coatings have little effect on the optical properties of crystals which still have excellent optical waveguide performance with the coatings.