Experiments of electrical stimulation were conducted to assess the electrode-immuno system property in American cockroach's neural system. The implanted electrode interface was monitored through Electrochemical Impedance Spectroscopy. Systematic increase in impedance against time was observed in all tests. Two mechanisms affecting the impedance of the interface were proposed: the formation of silver oxide and the encapsulation of hemocyte. Results of XAS showed existence of silver oxide at the interface. The magnitude of impedance at 1 kHz has significantly increased in 24 h post-implant for stimulated samples, which suggests the formation of hemocyte encapsulation. The increment of encapsulation layers shapes the semi-circle arc at high frequencies in the Nyquist plot. Circuit model of electrode-immuno system impedance was generated to interpret in vivo behavior. The data and the model suggest that the changes transport path is directly affected by cellular development on the electrode surface. Through predictable relationships between impedance measurement and insect's immuno-reaction, the impedance measurement can provide the assessment for designing hybrid robotic device. (C) 2012 Elsevier Ltd. All rights reserved.