Background. A statistical model was developed in this study to describe lactic acid production through a fermentation process of carrot in a rice bran bed by Lactobacillus plantarum. Materials and methods. Response surface methodology (RSM) based on Box-Behnken design was employed to statistically evaluate and optimize the conditions for maximum lactic acid production. Results. The significance and interaction of salt concentration, water and initial L. plantarum starter density on final lactic acid content were found. With the use of the developed quadratic model equation, a maximum achieved lactic acid content of 1.35% was obtained in a rice bran bed fermentation process at optimum operating conditions of approximately 2.95% salt, 48.24% water and 2.9 log cfu/g of L. plantarum. After fermentation, the amount of total polyphenol content, antioxidant activity and carbohydrate had increased while the β-carotene in carrot was significantly retained (92.84%). Conclusion. The above results could provide a practical basis for the fermentation process in rice bran bed to produce a delicious and reliable product using L. plantarum strain XK 1.4 which could be a significant contribution to the food industry