Abstract: Since the signals were obtained by line CCD in digital level measurement, field range and resolution was restricted because of great changes in viewing distance. It is very difficult for level meter to code and decode. A new coding and decoding method is proposed. Based on area-array CCD, this solution uses mixed coding technology and takes advantage of two-dimensional signal. The tradeoff between a lack of barcode samples when distance is too short and low resolution of image when distance is too long was overcome, and the key technical problem was completely resolved. By optimizing the algorithm, we also achieved real-time online measurement. The results show that measurement of absolute error is between -1mm and 1mm when measuring range is between 2m and 10m, which proved that the proposed method is correct and feasible.