Objectives: This study was aimed to optimize the cellulose content (CC) increase with the percentage removal of hemicellulose (HC) and lignin content (LC) of shell butter bark wood fiber (SBBWF) by alkalization process. The truth remains that natural fibers have many uses to be employed in all human activities. The minimization of plant waste is a secret for close economy by effectively converting it to useful ventures. Methods/findings: The SBBWF was inserted in variant solutions for the concentration of sodium hydroxide (CSH) at 3–9 wt% and the soaking time (ST) for 6–18 h. The SBBWF before and after pretreatment were analyzed through gravimetric method and Fourier transform infra-red (FTIR) to determine its composition and organic substance with corresponding functionality, respectively. The optimization was examined using the central composite design (CCD), an option in response surface methodology (RSM). The results at optimal conditions indicated that the increment in CC with the reduction of HC and LC was 97.9988%, 44.5245%, and 45.716%, respectively. The factors at this junction were CSH and ST at 3 wt% and 18 h, respectively. The R2 values of CC, HC and LC had an approximation nearer to 1. The errors approximated by RSM and experimental readings were <0.43%. Application: Therefore, the modified SBBWF at this state is potential material in the component of composite manufacturing to be applied in domestic utilization.