Goat's milk is processed into kefir with the hope of eliminating the smell of "strong, goaty odour" and extending the shelf life of goat's milk. Kefir is a probiotic drink whose growth can be optimized with the addition of prebiotics in the form of "Bile" bananas. This study aimed to determine the effect of the maturity level of "Bile'' bananas on the microbiological, chemical, and sensory quality of goat's milk kefir. This study used a completely randomized design with one factor (difference in the maturity level of "Bile '' bananas : green, yellowish green, yellow, speckled yellow and brown) which repeated 4 times to obtain 20 experimental units. The parameters tested were the degree of acidity (pH), total titrated acid, viscosity, total Lactic Acid Bacteria, viability of Lactic Acid Bacteria and sensory quality including aroma, taste, color and viscosity. The results showed that the maturity level of "Bile" bananas had a significant influenced for all parameters tested. The yellow "Bile" banana maturity level treatment was the best treatment based on pH value 4.37; total acid number 4.68%; viscosity 65,750 cP; Lactic Acid Bacteria growth was 8.48 log CFU / ml and decreased Lactic Acid Bacteria viability 0.47 log CFU / ml as well as sensory properties by scoring and hedonic that can be accepted by the panelists.