In order to develop a substation protection room patrol robot equipment suitable for power grid users, a digital identification method based on support vector machine (SVM) for digital display instrument of substation protection room is proposed, which is used to automatically identify and monitor the digital instrument data captured by the robot. Firstly, a custom threshold segmentation is performed on the image taken by the robot, and the minimum circumscribed rectangle of the connected domain is searched for the digital display instrument region in the image. Then the gray scale, median filtering, image enhancement, digital segmentation, adaptive binarizationand normalization operations are sequentially performed on the acquired digital display instrument region, implementing preprocessing of the digital instrument area to obtain a single number. Finally, a single digital image block processed by the decimal point is input into the constructed multivariate SVM classifier to implement the identification of a single number. The experimental results show that the proposed method can achieve 96.5% correct recognition rate and can be used for intelligent inspection of small patrol robots in substation protection room.