Objective:To study the biting force of upper premolar and molar in the patients with unilateral cleft lip and palate(UCLP).Method:25 health people and 22 cases (13 male and 9 female with pemanent teeth) of UCLP without tempromandibular joint dysfuction were selected in the subject.Their biting force of upper premolar and molar in intercaspid position was tested by MBF 1 device,meanwhile,their mastictory perfomance and contact area of upper premolar and molar were checked.All of the results were managed by computer with SPSS 7.5 statistics software.Results:①Biting force of upper premolar and molar of male was higher than that of female in health people,but there was no sexual difference in UCLP.② Biting force in the group of UCLP was lower than that in the control (P