This study aims to determine the potency of the combination formulation of Tambora leaves, Sembalit Angin leaves and turmeric rhizome using a 1: 2: 3 combination formulation and to determine its inhibitory power against the growth of Escherichiacoli bacteria in vitro which is measured based on the width of the inhibition zone or clear zone from the outermost side aper disc containing methanol extract, a combination formulation of Tambora leaves, Sembalit Angin leaves, and turmeric rhizome with Escherichiacoli bacteria colonies on the surface of the Na plate medium. Data collection and measurement of the growth of Escherichiacoli bacteria were carried out during the incubation period of 1x24 hours, 2x24 hours and 3x24 hours. The data obtained were then analyzed using the Anava one way analysis statistical test and continued with the 1% Duncan test. The results found that the combination formulation of 1: 2: 3 bioherbal methanol extract of Tambora leaves, Sembalit Angin leaves, and Turmeric rhizomes had a significant effect on the growth of Escherichiacoli at 1% significance, as evidenced by the sig value. 0.00 <0.01, so the 1: 2: 3 combination formulation can be recommended as the most effective combination extract formulation in inhibiting the growth of Escherichiacoli bacteria.