Enzymes catalyze various oxidation and reduction reactions for biosensors and biofuel cells, but their successful applications are often hampered by poor enzyme stability and low electron conductivity. In this study, we report the synthesis of crosslinked polymer network, directly grown from the surface of glucose oxidase, via two-steps of surface activation and atom transfer radical polymerization (ATRP) to prepare ATRP-SEG. As a result, the half-lives of ATRP-SEG under incubation at 50 ºC were 6.2 d, which is 78 times longer than that of free GOx enzyme (1.9 h). For the improvement of electron mediation in the enzyme electrode, the same polymerization of ATRP-SEG was performed, but by adding vinyl-ferrocene from the beginning, to prepare Fc-ATRP-SEG with conjugated ferrocene. The sensitivity of Fc-ATRP-SEG electrode is 110 μ-A (cm2 mM)−1 that is 295 and 1274 times higher than those of native GOx and ATRP-SEG, respectively. This protocol of ATRP-SEG is a powerful tool not only to control the thickness of polymeric network while achieving stabilization of a single enzyme, but also to improve the conductivity by simply adding vinyl-ferrocene in the beginning. This new protocol is anticipated to be employed to stabilize various other enzymes while controlling the thickness of polymeric network, in other words, mass transfer limitation. The protocol of adding vinyl-ferrocene can be expanded to many other electron mediators in order to improve both enzyme stabilization and electron transfer at the same time.