Electro-conductive carbon black filled polyisoprene rubber shows large reflexive piezoresistive effect – electrical resistivity changes due to applied pressure. The reason for this holds three dimensional electro-conductive net, which restructures in time – inter-particle separation changes at low applied pressure and electro-conductive channels disrupt at higher pressures [1]. Reflexive abilities of piezoresitive effect mostly depend on mechanical properties of polyisoprene rubber matrix. When loding/unloading the composite, polyisoprene macromolecules change their conformation in space, promoting the motion of filler particles in rubber matrix, hence decreasing overall electric resistivity of composite. Rubber exhibits viscoelastic properties as creep, recovery and stress relaxation, so this implies time dependence of piezoresistance [2]. One of the main aspects is the recovery of electrical resistance after unloading, which we call the relaxation of piezoresistance. The possible tree relaxation mechanisms of piezoresistance have been discussed in comparison with relaxation of mechanical deformation.