Aloe vera has been proven as anti inflammatory effect, but the lowest concentration and the shortest time of Aloe vera which could decrease inflammatory has not been known exactly. The aims of this research is to find the lowest concentration on 1 day application of Aloe Vera which could decrease inflammatory on rat oral mucosa after it has been applied by H2O2 10% for 3 days. 12 rats that has been applied by H2O2 10% were divided into 4 groups, which are : applied Aloe vera 10% substrate for 1 day (3 rats), applied Aloe vera 25% substrate for 1 day (3 rats), control group 1 which applied Aloe vera 10% substrate for 3 days (3 rats), and control group 2 which applied Aloe vera 25% substrate for 3 days (3 rats). The score of inflammatory is determined using modification the method of Eda S and Fuyama. The obtained data were analyzed with Kolmogorov - Smirnov (p<0,05). In conclusion, Aloe vera substrate 10% applied for 1 day could decrease oral mucosa inflammatory.