OBJECTIVE To investigate the classification of alar base depression, so as to provide the reference for the surgical management of secondary nasal deformity of unilateral cleft lip. METHODS From Jul. 2008 to Feb. 2009, 26 cases with secondary deformity of unilateral cleft lip were treated. All the patients underwent 3-dimensional CT for maxillary measurement. The nasal soft tissue measurement was performed pre- and post-operatively. The relationship between the maxillary and soft tissue at alar base was analyzed. The nasal deformity was classified. RESULTS The location of alar base was not related to the form of piriform aperture, but the bony defect at the alar base was correlated to the patient satisfactory. The nasal deformity was graded as I when the depression at alar base was less than 4.5 mm in depth, as II when it was 4.5-5.0 mm in depth, and as III when it was more than 5 mm in depth. The deformity could be corrected with only soft tissue plasty for grade I, with soft tissue plasty or artificial implants for grade II, with combined bone autograft or alveolar cleft repair for grade III. CONCLUSIONS The depression at maxillary does not necessarily result in alar base depression. The alar base can be adjust to proper position through operation. The operation should be designed based on the preoperative nasal measurement.