OBJECTIVE： To optimize the formulation of Diosmin gel and to investigate its in vitro release property. METHODS： Diosmin gel were prepared by using Carbomer 940 as matrix. Using accumulative release rate as index， with the amount of Carbomer 940， ethanol， acetone and pH as factors， L9（34） orthogonal test was conducted. The formulation of Diosmin gel was optimized and validated. Using Diosmin ointment as reference， dialysis bag diffusion method was used to investigate in vitro release property of Diosmin gel prepared by optimal formulation. RESULTS： The optimal formulation of Diosmin gel included Carbomer 940 1.5 g， ethanol 15 mL， glycerol 8 g， pH 6. The gel prepared with optimal formulation was sticky brown-yellow semi solid， and had good coating and spreading properties. The average accumulative release rate （2 h） was （12.67±0.12）％. Results of drug release test showed that Diosmin gel released rapidly within 12 h， then gradually slowed down. The accumulative release rates were （71.93±0.42）％ （12 h） and （80.47±0.54）％ （24 h）， drug release of which were in line with Higuchi equation. Diosmin ointment was released slowly. The accumulative release rates were （41.74±0.18）％ （12 h） and （62.63±0.59）％ （24 h）. Drug release of it were in line with first-order equation. CONCLUSIONS： The formulation of Diosmin gel is optimized successfully. Prepared Diosmin gel has good drug release property.