The relation between conductivity σ(Ta) and temperature T has been investigated experimentaly for the samples with different structure under phase transition. We have found anomalous phenomenon on superconducting transition R(T) curves corresponding to some special phase transition zones as the samples crystallize into metastable intermediat phase.In this paper, a mixed state model is suggested, in which the metastable metal-phase and the quasi-semiconducting phases are mixed. Based on this model, the anomalous phenomenon can be explained and the theoretical calculations is carried out. The theory is in agreement with experimental data fairly.