The research aimed to study black grass leaves extract immersed in edible coating, i.e. chitosan to prevent microbial attack on tomatoes. The extract was obtained from black grass leaves using maseration method. The experiment was designed with Completely Randomized Design using three treatments as follows: 1. chitosan 1,5%. (2) chitosan 1,5 with combined Ekstraks black grass leaves each is equal to 5 % . 10 %, 15 %, 20%) Chitosan mixed with extract black grass leaves and used as edible coating. Analysis used to test the quality of tomatoes, hardness, weight loss, colour, titrable acid,acorbic acid, sugar and microbial attack. Result showed that chitosan mixed with extract of black grass leaves and used as edible coating gave the best result in maintaining quality of tomatoes based on analysis on hardness, weight loss, colour, titrable acid; acorbic acid and sugar. Extract black grass leaves was succeed in prolong the shelf life on tomatoes