A theoretical and experimental study on extracting channel carrier concentration for 4H-SiC buried channel MOSFET has been carried out. The distortion of C-V curve caused by the existence of p-n junction in buried channel MOS structure would affect the extracting result, and the interface states on SiO2/SiC interface make extracting result deviate from true channel carrier concentration. In this paper, firstly, a theoretical analysis about the effects of channel depth and interface state on extracting result is made. Then the C-V curves for buried-channel MOS structure with two different channel depth are presented from which the channel carrier concentration is extracted. In the measurement of C-V curves, three different sweep velocities are used to analyze the effect of interface states. The theoretical results agree with experimental results.