In order to understand the adaptation mechanism of olive to cold stress,we investigated cold stress (5 ℃,0 ℃,-5 ℃,-10 ℃) and ordinary temperature culture(18 ℃,control) with in vitro leaves of 6 olive varieties which planted at Longnan District,Gansu Province.The physiological and biochemical index related with cold hardiness were measured.By the method of subordinate function,comprehensive evaluation on the cold resistance of different varieties was made.The results indicated that:(1)The in vitro leaf relative conductivity of different varieties increased as temperature decreased,presenting “S” type curve change pattern.By using the logistic equation,the half lethal temperatures of the 6 olive varieties were obtained.The values were between -6.687 ℃~-3.706 ℃,and increased according to ‘Picholine’＜‘Pendolino’＜‘Leccino’＜‘Ascolana Tenera’＜‘Ezhi 8 ’＜‘Frantoio’ sequence.(2)The in vitro leaf chlorophyll contents of olive varieties decreased gradually as stress temperature decreased gradually,while the soluble sugar content generally increased,meanwhile the contents of soluble protein,proline,malondialdehyde (MDA) and the activities of SOD,POD,CAT generally increased first and then decreased.(3)Under -10 ℃ cold stress,compared with normal temperature control,the leaf chlorophyll contents of ‘Picholine’ and ‘Pendolino’ declined slightly,the osmoregulation substance contents and protective enzyme activities increased greatly,and MDA contents increased slightly,meanwhile ‘Frantoio’ and‘ Ezhi 8’ were reversely varied.(4)The 6 olive varieties cold resistance order(‘Picholine’＞‘Pendolino’＞‘Leccino’＞‘Ascolana Tenera’＞‘Ezhi 8 ’＞‘Frantoio’ ) was identified by the average degree of membership hardiness (cold resistance comprehensive evaluation value) was in contrast with that of the half lethal temperature order.The results indicated that,under cold stress,‘Picholine’ and ‘Pendolino’ could relieve the stress of peroxide damage by increasing the osmoregulation substance contents and protective enzyme activities,showed stronger cold resistance ability.Both the half lethal temperature based on relative conductivity and the comprehensive evaluation based on subordinate function analysis could accurately appraise cold resistance of olive varieties.