Interest in bio-imprinting techniques has increased because it allows some stability characteristics of enzymes to be improved. In this study, we developed a simple way to improve the thermal and pH stabilities of ascorbate oxidase biosensor. The membrane of a Clark oxygen electrode was coated by a bioactive layer containing ascorbate oxidase and gelatin cross-linked by glutaraldehyde. Citrate was used to imprint the ascorbate oxidase molecularly. The optimum temperature and pH of both unmodified and citrate modified biosensors were investigated, by comparing their resulting stability. Also, calibration graphs and operational stabilities were compared with each other. The results showed that this simple way should be used to improve the stabilities of a biosensor.