Synthesis of isoprene so far formed from polymer conversion occurs at temperatures above 400oC with a percentage of less than 20% isoprene composition and is prone to forming other compounds such as aromatic compounds. This study aims to see if the use of K2O/KNO3 in converting natural rubber into isoprene will increase conversion and take place at low temperatures. KNO3 can keep the formation of other side products with a composition of %, which aims to stabilize the catalyst to isolate the formation of isoprene. The results showed that variations in the amount of catalyst, temperature, and solvent in the cracking reaction significantly impacted the final result of isoprene synthesis. At 90oC, with the amount of catalyst 3 g, a conversion of 86.86% was obtained. This was due to the role of KNO3 in stabilizing and increasing the catalytic activity of the catalyst. At 130oC, it produced a conversion of 1.5 g 81.58%. K2O/KNO3 catalyst can be amphoteric, basic or acidic influenced by the operating temperature. K2O/KNO3 catalyst in alkaline conditions has high stability and catalytic activity and can produce better conversion with low temperatures in natural rubber cracking to produce isoprene.