Abstract: The 20CrMnTi carburizing hardening depth was detected and characterized by nondestructive testing of magnetic coercive force. The magnetic coercive force was detected and analyzed for samples with different depths of carburizing layer and it was found that the magnetic coercive force was to increase with the increase of the depth of carburizing layer, whereas the increase became slower while the depth of the carburizing layer reached some certain extent. The reliability and error of the results obtained by the method of magnetic coercive force are analyzed in comparison with the method of metallography. Experimental and analytical results show that the method can be used for the detection of the depth of the carburizing layer.