Through experimental research,an automatic measuring instrument has been developed based on laser sensors.The measurement process and data can be visualized in real-time through Bluetooth data transmission.The automatic measuring instrument can be extended into the cylinder through the connecting pipe for 360° scanning measurement,solving the measurement difficulties of the pressure vessel which are unable to enter the interior.The accurate measurement can be achieved without overlapping the central axis of the measuring rod and the cylinder,also the uncertainty difficulty of whether the measurement data comes from the same diameter cross-section of the container was overcame by an intelligent algorithms.After the verification of pressure vessels with an inner diameter micrometer measuring 800~1 600 mm,the conclusion can be confirmed that the measurement results of the inner diameter automatic measuring instrument are accurate and reliable with the relative error less than 0.17%.