Introduction: Cellulose nanocrystals are modified through integration with various polymers for a wide range of applications, one of which is for biomedical applications. Materials and Methods: The process involves alkalization, bleaching, varying the duration (3, 4, or 5 hours), temperature (50°C, 70°C, or 90°C) and, acid hydrolysis. Results.:The results show that the crystallinity index of the cellulose nanocrystal increases with the stages of alkalinization, bleaching and acid hydrolysis. Untreated fibers had a relatively high impurity content, including lignin, hemicellulose, and wax, a crystallinity index of 41.25% and a degradation temperature of 290 °C. Heating temperature lowers the crystallinity index of cellulose. Conclusion: The isolation method with the stages of alkalinization process, bleaching for 4 hours, heating temperature of 70 °C and acid hydrolysis is the optimal method in producing crystalline cellulose with low impurity level, high crystallinity (80.25), fine fiber morphology, and degradation temperature 310oC. © 2025 Universiti Putra Malaysia Press. All rights reserved.