In this paper,we reported the physiological and cell ultra-structure changes in leaves of one-year old Passiflora edulis cane under -6℃ cold stress treatment.Our results demonstrated that:(1)Relative electrical conductivity (REC),contents of MDA and H₂O₂ in leaves of room temperature treatment group increased under -6℃ cold stress,but REC and MDA contents in leaves of cold-hardening treatment group declined 24.79% and 49.29%,respectively,after 12 hours or 72 hours treatment comparing to room temperature treatment group.(2)The content of H₂O₂ in room temperature treatment group increased 1.20 folds at 48 hours treatment comparing to 0 hour treatment and increased 1.14 folds at 48 hours treatment comparing to cold-hardening treatment group.(3)Proline content was detected to increase during treatment and the content of cold-hardening treatment group increased 15.48% than that of room temperature treatment group after 72 hours treatment.(4)Cold-hardening treatment group enhanced cold tolerance in P.edulis through activiting antioxidative system,such as,POD,CAT,SOD.The activities of the three enzymes were showed to reach peak after 12 hours (POD) and 24 hours (CAT,SOD) of treatment,then decreased.(5)We observed phenomena as chloroplast granas tumidness,karyothecas disappearing and plasmalemma invagination in room temperature treatment group under the electronic microscope.These symptoms were not very obvious at 24~48 hours of treatment,but turned to be serious after 72 hours cold stress.The degree of cold hurting to chloroplasts in cold-hardening treatment group were lighter than that in room temperature treatment group.The results obtained from this study hinted that cold-hardening treatment could help to increase cold endurance for P.edulis.