The formulation of microcapsule of methyl-metsulfuron using biopolymer of poly(3-hydroxy-butyrate) as matrix of herbicide by solvent evaporation technique has been carried out. In the study, three types of the microcapsule formulation was used with the ratio between methyl-metsulfuron, and poly(3-hydroxybutyrate) of 2:1, 1:1, and 1:2 respectively. The particle distribution was measured using a calibrated microscope. Active substance release was determined by UV-Vis spectrophotometer. Results indicated that biopolymer of poly(3-hydroxy-butyrate) can be used as the matrix polymer for slow release preparations and influence the release of active substance of metsulfuron-methyl in the objects. It is also observed that the highest value of recovery test of active compound was formula 1 : 83.56%, followed by formula 2 : 71.22% and the last was formula 3 : 67.79% The kinetic model of active compound released from microcapsules with correlation coefficient of near by 1 and followed the zero order kinetic obtained from formula 1.