The measurement of carrier mobility in organic semiconductor material and device is one of important study contents. The hole-only devices based on the different solvent blends of poly (3-hexylthiophene) (P3HT) and [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) as acceptor are fabricated, the structures of the devices are all ITO/PEDOT:PSS/P3HT:PCBM/Au. The hole mobilities in the blend systems with different solvents and various annealing treatments are measured by the space charge limited current method. The results show that the J-V curves of charge transfer in the devices meet Mott-Gurney equation, the hole mobilities in the active layer with different solvents are different, the active layer formed with high boiling point solvent 1, 2-dichlorobenzene possesses higher hole mobility, heat treatment contributes to the improvement of the hole mobility in the devices. The reason of change of hole mobility is analyzed.