In this work, activity of immobilized phytase on blended polyacrylamide (PAAm)/starch nanofibers produced via electrospinning was optimized by computer-aided statistical method of experimental design, response surface methodology (RSM). Thereafter, the role of polymer concentration and percentage of starch in period of enzyme activity were optimized using RSM. We employed these two polymers in blend format as two types of hip-compatible and biodegradable materials including sufficient chemical groups to be appropriate candidates for biological applications. Cross-linking treatments were performed using 3-aminopropyltriethoxysilan (APTES) and glutaraldehyde (GA), and finally phytase enzyme was successfully immobilized on the surface of membranes. First, we used scanning electron microscopy for morphological observation of blended nanofibers. According to the results obtained from response surface method and mean effect assessment, PAAm concentration and percentage of starch as process variables in the experimental design were successfully able to influence the biological properties of immobilized enzyme. Besides, it is also supposed that the presence of starch as a biodegradable and biocompatible natural polymer has a great effect on increasing the unit of enzyme's activity on the membrane surface.