ObjectivesThis study aimed to establish a simple and practical classification to guide the clinical treatment of diastasis recti abdominis (DRA) based on ultrasound characteristics with different severities of DRA, and to verify its clinical utility.MethodsWe retrospectively enrolled 301 DRA patients as pilot cohort and divided into Conservative Treatment Group and Surgical Group according to clinical outcomes. A new Width–Length classification was summarized based on ultrasound measurements of the width and length of midline separation. Then, 100 DRA patients were enrolled prospectively as validation cohort, and diagnostic performance was evaluated by clinical treatment.ResultsThe Width–Length classification in pilot cohort was as follows: Type 1 (n = 108), open only at M3; Type 2 (n = 63), open at M3 and either M2 or M4 (inter‐rectus distance at M3 <47 mm); Type 3 (n = 44), open at M3 and either M2 or M4 (inter‐rectus distance at M3 ≥47 mm); Type 4 (n = 74), open at M3, along with other two sites of M1, M2, M4, or M5; Type 5 (n = 12), open at M2, M3, and M4, along with M1 or M5, or both. DRA patients in Type 1–2 were recommended for conservative treatment, and in Type 3–5 were recommended for surgical treatment (all P < .05). In the validation cohort, the accuracy of Width–Length classification in determining treatment strategy was 86.0%.ConclusionsThis study proposes a Width–Length classification based on the width and length of midline separation on ultrasound, which was validated to be simple, practical and effective in guiding DRA treatment.