Objective: To determine the appropriate cone depth for treating high grade precancerous lesions to achieve negative pathological margins of cones from LEEPs. Other factors associated with positive pathological margin were also investigated. Methods: A Retrospective study recruited 170 patients who received indications for LEEP during January 2015 to July 2020 were enrolled. The participants were operated by a single cut of LEEP and not had previously conization before. All patient data were collected into two groups, including negative and positive cone margin groups. Then, we used the cone depth by calculating from cone tissue after formalin fixation to eliminate shrinkage effect. The appropriate cut-off points for cone depth were calculated by ROC and analyzed factors that influence positive cone margin. Results: The depth of cone (mm ±SD) of negative margin group was 8.70 (±3.36) and 6.13 (±2.28) mm in positive margin group. The appropriate cut-off points for cone depth were calculated by ROC presented at resection depth of 7.21 mm, which displayed proper cone depth with a sensitivity of 63.53% and specificity of 71.76%. Elderly age (adjusted OR 1.061, 95%CI 1.008-1.117, p=0.002), number of quadrants of lesion involvement (adjusted OR 1.182, 95%CI 1.312-2.513, p=<0.001) and glandular involvement (adjusted OR 3.648, p=0.002) were the significant risk factors for positive margin. Conclusion: The appropriate cone depth for treating high grade precancerous lesions was at least 7.21 mm to achieve a negative cone margin from LEEP. The significant factors associated with positive cone margin include elderly age, more quadrants of lesion involvement and glandular involvement.