Objective The purpose of this study was to explore the diagnostic value of blue laser imaging (BLI) combined with micro probe endoscopic ultrasonography (EUS) in predicting the depth of early colorectal tumor invasion. Methods This clinical study is a single-center, retrospective study from the General Hospital of the Western Theater Command of the Chinese People’s Liberation Army.289 patients with early colorectal cancer (CRC) diagnosed by colonoscopy and histopathological examination from January 2018 to December 2020 were included. The patients completed BLI-ME and/or EUS examination and judged the depth of invasion before receiving endoscopic or surgical treatment. Randomly divide the patients into three groups. Group A was treated with blue laser imaging technology, group B was treated with endoscopic ultrasonography, and group C was treated with blue laser imaging technology combined with endoscopic ultrasonography. Results the patients were divided into the two groups: mucosa to superficial submucosa (m-SMs, infiltration depth＜1000μm) or deep submucosa (SMD, infiltration depth≥1000μm). The sensitivity, specificity and accuracy of three groups of patients with different endoscopic modes on the depth of invasion of early colorectal cancer were compared and analyzed. The consistency of different endoscopic diagnosis results and pathological results was compared. Univariate analysis of consistent group and non-consistent group, influencing factors of inconsistent results between groups, and the examination time and subjective feelings of patients in group A and group B were compared and analyzed (1~10 points). Results the diagnostic accuracy of blue laser imaging technology combined with micro probe EUS was better than that of blue laser imaging technology group and micro probe EUS group. The consistency of blue laser imaging combined with micro probe EUS and pathological diagnosis (kappa=0.761) was better than that of blue laser imaging group (kappa=0.576) and micro probe EUS group (kappa=0.574). Univariate analysis showed that there were significant differences in age, lesion size, gross shape and infiltration depth between the two groups (P＜0.05), it may be the influencing factor that the results of endoscopic diagnosis are inconsistent with those of pathological diagnosis. The time of blue laser imaging was significantly shorter (P＜0.05), and the subjective feeling of patients was significantly better than that of EUS. Conclusion BLI combined with micro probe EUS has higher accuracy in predicting the invasion depth of early colorectal cancer, and the examination results are accurate and reliable, which has good clinical application value in the preoperative evaluation of early colorectal cancer.