Abstract: An investigation of Isothermal Decay Current (IDC) method on determining trap parameter has been made on the α-copper phthalocyanine evaporated films at different temperatures and electric fields. It shows that the trap behaves like a distributed trap of depth 0.58 eV and attempt-to-escape frequency 1.7×10⁸ s^-1. The field dependence of IDO current indicates a field assisted detrapping probably in the sense of Poole-Frenkel mechanism.