Photoconductivity properties of ordinal multiwalled carbon nanotubes(MWNTs) have been studied.The large area ordinal MWNTs are obtained by chemical vapour deposition at 720 ℃ on silicon substrate.Experimental results indicate that under normal condition,the photocurrent is dominated by the transport of charge carriers.The increase in concentration of charge carriers stimulated by the applied laser results in a measurable photocurrent rise that depends almost linearly on the applied bias voltage and the laser power,when the power is low.