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The purple sweet potato extract-supplemented synbiotic yogurt as a prebiotic and Lactobacillus plantarum Dad 13 isolated from buttermilk as a probiotic offers the potential as a functional food, in spite of its storage in low temperature. A freeze-drying technique requires a cryoprotectant as a protective agent for dairy products such as yogurt. The research aimed to determine the proper sucrose concentration as a cryoprotectant to obtain the chemical properties and the viability of Lactic Acid Bacteria and Lactobacillus plantarum. It adopted a one-factor Completely Randomized Design (CRD) by including sucrose in various concentrations from 0%, 2.5%, 5% to 7.5% through three replications.The results signified that various sucrose concentrations significantly affected the yields of the purple sweet potato extract-supplemented synbiotic yogurt, reduction-sugar level, the total of Lactic Acid Bacteria (LAB), and the total of Lactobacillus plantarum before and after the freeze-drying process, however, indicated no significant impact on the moisture content and total quantity of LAB. The best treatment to the synbiotic yogurt was induced through the addition of sucrose with a concentration of 5% as a cryoprotectant. The treatment signified the following characteristics: a 14.797% of yields, a 7.51% of water content, a 14.59% of reduction-sugar level, a 1.98x109 CFU/ml of total Lactic Acid Bacteria (LAB) before the freeze-drying and a 9.28x108 CFU/ml after the freeze-drying, a 8.23x108 CFU/ml of total Lactobacillus plantarum before the freeze-drying and a 6.81x108 CFU/ml after the freeze-drying.