Hole only devices were fabricated with the structure of ITO/PEDOT/P3HT （poly（3-hexylthiophene））/Ag. The capacitance-frequency characteristics of samples annealed at different temperatures were investigated by admittance spectroscopy technique. Hole mobilities were calculated and it was found that the hole mobility could be pronouncedly influenced by annealing. The hole mobility was enhanced to the 10-3 cm2/Vs order after annealing, while the hole mobility of the unannealed sample was just of 10-4 cm2/Vs order. The hole mobility of the annealed sample is almost unchanged under different electric field. In contrast, the hole mobility of the annealed sample showed relatively significant change with the electric field.