Simultaneous saccharification and fermentation (SSF) configuration offers an efficient used of the reactor. In this configuration, both the hydrolysis and fermentation processes are conducted simultaneously in a single bioreactor and the overall process may be accelerated. Problems may arise if both processes have different optimum conditions, and therefore process optimization is required. This paper presents the development of mathematical model over SSF strategy implementation for producing xylitol from hemicellulose component of lignocellulosic materials. The model comprises of the hydrolysis of hemicellulose and the fermentation of hydrolysate into xylitol. The model was simulated for various process temperature, prior hydrolysis time, and inoculum concentration. Simulation of the developed kinetics model shows that the optimum SSF temperature is 36oC, whereas conducting a prior hydrolysis at its optimum hydrolysis temperature will further shorten the processing time and increase the xylitol productivity. On the other hand, increasing the inoculum size will shorten the processing time further. For an initial xylan concentration of 100 g/L, the best condition is obtained by performing 21-hour prior hydrolysis at 60oC, followed by SSF at 36oC by adding 2.0 g/L inoculum, giving 46.27 g/L xylitol within 77 hours of total processing time.