A method of piping defect detection is provided. A semiconductor substrate having an active region and an isolation region is provided, a plurality of semiconductor elements are formed on the semiconductor substrate, a dielectric layer is deposited on the semiconductor substrate and the semiconductor elements, and first and second contact plugs are formed in the dielectric layer to connect the active region and the isolation region respectively. The first contact plug and the second contact plug are illuminated by an electron beam, accumulating charge on the second contact plug, and piping defects are detected between the first contact plug and the second contact plug according to brightness contrast between the first contact plug and the second contact plug.