The project studies the ability to withstand the tensile of bioplastics made from the starch of the tamarind seeds and longan seeds. Objective to study the production of bioplastics made from the starch of the tamarind seeds and longan seeds that have the ability to withstand tensile forces. The starch from tamarind seeds and longan seeds mixed with rubber, Copper (II) carbonate, Ammonia and Sulfuric acid to be a new substances by the ratio between the starch of seeds per timber is 1: 1 and 1: 2 and then dried at 45 ° C for 36 hours and cut to the size 5x6 cm, then put to the test by hanging scales, tensile springs and weight by sandbags. The results showed that bioplastics from the starch of the tamarind seeds have the ability to withstand high tensile forces than the starch of the longan seeds. The rubber will increase the ability to withstand higher tensile forces.