The invention provides an anti-virus sustained-release drug capable of being subjected to intraocular injection, a preparation method and applications thereof, wherein the anti-virus sustained-releasedrug is a foscarnet insoluble salt micro-crystal, and the foscarnet insoluble salt is the polyvalent metal salt of foscarnet. The preparation method comprises: carrying out a reaction on the monovalent metal salt of foscarnet and the soluble salt of a polyvalent metal in water to obtain the system containing the foscarnet insoluble salt micro-crystal. According to the present invention, based onthe special requirement of the controlled-release and slow-release intraocular injection, the foscarnet insoluble salt micro-crystal slow-release system is designed, wherein the nominal drug loading can be more than 100%; the foscarnet insoluble salt micro-crystal slow-release drug can be lastingly, stably and slowly released in the vitreous cavity of rabbit eyes, the concentration of the foscarnet in the vitreous cavity is always maintained above the effective therapeutic concentration of sodium foscarnet, the sustained release period is up to 12 weeks, and the drug does not have obvious toxic effects and inflammatory reaction; and the foscarnet insoluble salt can be used as the anti-virus sustained-release drug capable of being injected into the vitreous cavity.