Invertase was immobilized into photographic gelatin by chemical crosslinking with formaldehyde and chromium (III) acetate. Polyester film strips were coated with invertase-gelatin mixture which increased durability during consecutive immersions into reaction media. The effect of gelatin, crosslinker and enzyme concentrations on activity were studied. Enzyme leakages from immobilized invertase film strips were controlled by washing with EDTA solutions. The activities of washing solutions were measured spectrophotometrically to determine unbounded enzyme concentration. Effect of use number on activity was also determined. Percent activity of immobilized invertase was lower than that of free enzyme. The activity however retained even after 10 washings (170 minutes) followed by 9 use in 18 weeks.