In order to ensure the operating security of pressure containers, the P. R. China make a corresponding standard of producing, checking and accepting pressure containers, in which the weld stagger joint is an importance parameter to be measured. Because the zero scale is fixed, the existing mechanical stagger joint measuring scale has scoring error of scale, zero error, visual error and cumulative error, it is not convenient to read and easy to get wrong data, resulting in misjudgment and other defects. The existing capacitive displacement sensor based instrument with digital display for measuring welded joint angularity and stagger is the parameter detection after the weld completed, it cannot be used for detecting welded joint stagger joint before welding, so it is not convenient to adjust the weld and control the welding quality. To make up for the lack of existing measurement tools, we developed a capacitive displacement sensor based portable instrument with digital display for measuring weld stagger joint. This paper introduces its structures and principle. Through error analysis, calculation and experimental testing, the integrated error of the instrument is less than 0.03 mm, the measuring accuracy can meet the requirements prescribed by the GB150-1998 standard.