The kinetic study of the anionic polymerization of isoprene is carried out in tetrahydrofuran(TMF), using n-BuLi as initiator. Kinetic parameters are obtained, which comprise chain propagation rate constant, k(p) and partial rate constants, k(3) and k(4) + k(5), propagation orders with respect to monomer and active species concentrations, alpha and-beta, real activation energy, E, as well as partial activation energies, E-3 and E4+5 and so on. The relationship between the microstructure of polyisoprene and the ratio of [THF]/[n-BuLi] has been investigated. On the basis of the studies mentioned above, a reasonable mechanism of the anionic polymerization of isoprene in THF is proposed.