OBJECTIVE：To prepare supersaturated system of lip ophilic aci clovir（ACV）prodrug，and to increase the cutaneous bioavailability of ACV. METHODS ：Three prodrugs of ACV were synthesized by anhydride acylation ，i.e. aciclovir acetate （ACV-Ace），butyrate（ACV-But）and hexanoate （ACV-Hex）. The structures of ACV and three ACV prodrugs were confirmed by 1H-NMR and HRESI-MS ；the concentrations of ACV and three ACV prodrugs were determined by UPLC-triple quadrupole tandem mass spectrometry ，and saturated solubility of them in different volume fractions of propylene glycol-water solution was calculated. The compound with the greatest potential of form supersaturated system was screened out. The supersaturated system of that compound was prepared by co-solvent method. The effect of hydroxypropyl methylcellulose E 3 （HPMC E 3） on its physical stability was observed by light microscope. Vertical Franz diffusion cells were used to study the effects of degree of supersaturation （DS）and HPMC E 3 on the deposited amount of drug in the excised porcine skin after using the supersaturated system for 1 h. The distribution of ACV in the excised porcine skin was determined by frozen slicing stratified quantitative method after using the supersaturated system and marketed aciclovir cream for 1 h. RESULTS ：Three ACV prodrugs were successfully synthesized. The established quantification methods met the requirements of biological sample analysis. Among all of the three ACV prodrugs ， ACV-Hex showed the lowest saturated solubility in water [ （0.5±0.0）mmol/L] a nd the highest saturated solubility in propylene glycol [（53.4 ± 14.2）mmol/L]，which made it potentially feasible to form supersaturated system with high DS. In 10％propylene glycol-water system ，the addition of HPMC E 3 163.com enabled ACV-Hex supersaturated systems ，with DS no morethan 4，to maintain physical stability within 1 h. The total deposited amount （ACV + ACV-Hex ） in skin after the application of ACV-Hex supersaturated system with DS of 4 for 1 h was higher than that after the application of ACV-Hex supersaturated system with DS less than 4 or without HPMC E 3. In addition ，the concentration of ACV in the basal epidermis （skin thickness was 100-160 mm）by supersaturated system was significantly higher than that of the marketed aciclovir cream （P＜0.05）. CONCLUSIONS：ACV-Hex，the lipophilic prodrug of ACV ，can form stable supersaturated system with DS of 4 in 10％ propylene glycol-water system in the presence of HPMC E 3. High concentration of ACV could be accumulated in the basal epidermis after the skin was exposed to supersaturated system for 1 h，which may be valuable for local treatment skin infection of herpes simplex virus .