Abstract: The effects of the testing personnel and machining methods on the determination accuracy of carburizing and carbonitriding quenching hardened layer depth were studied through experiments. The results show that the consistency of the repeated tests of the same material by the inspectors was qualified, and the test results of the depth of quenched hardened layer were within the range of good values; however, several machining methods such as grinding wheel cutting, grinding machine and wire cutting had a greater impact on the test results of the depth of quenched hardened layer, among which grinding machine and wire cutting had greater influence than cutting of grinding wheel.