Abstract: ObjectiveEffects of different rootstocks on grafting affinity, growth vigor, and photosynthetic characteristics of young Guiqi 1 navel orange trees were observed to provide references for determining its matching rootstock. MethodGuiqi 1 navel orange was grafted on six rootstocks (Shandong Poncirus trifoliate, Huapi Fortunalla margarita, Guizhi 1 Poncirus trifoliate, Daxin Citrus reticulata, Longzhou Citrus limonia, and Jinbao Citrus reticulata) to observe its grafting affinity, growth situation and diurnal changes of photosynthesis. ResultGuiqi 1 navel orange and Jinbao Citrus reticulata exhibited poor affinity. The affinity between Daxin Citrus reticulata and Guiqi 1 navel orange was the best. The grafting compatibility between Guiqi 1 and Longzhou Citrus limonia or Huapi Fortunalla margarita was good. There was medium grafting compatibility between Shandong Poncirus trifoliata or Guizhi 1 Poncirus trifoliata and Guiqi 1. However, big foot phenomenon occurred when Guiqi 1 navel orange was grafted on Shandong Poncirus trifoliata or Guizhi 1 Poncirus trifoliate and their grafting affinity was moderate. Different rootstocks and ages played different roles in the growth of Guiqi 1. There were unimodal, bimodal or mul-timodal curves of Pn diurnal variation of rootstock-scion combinations. The photosynthetic capacity of rootstock-scion combi-nation from high to low was Guiqi 1/Guizhi 1 Poncirus trifoliate, Guiqi 1/Jinbao Citrus reticulata, Guiqi 1/Shandong Poncirus trifoliate, Guiqi 1/Daxin Citrus reticulata, Guiqi 1/Huapi Fortunalla margarita, and Guiqi 1/Longzhoutu lemon. The water use efficiency of rootstock-scion combination from high to low was Guiqi 1/Jinbao Citrus reticulata, Guiqi 1/Huapi Fortunalla mar-garita, Guiqi 1/Guizhi 1 Poncirus trifoliata, Guiqi 1/Daxin Citrus reticulata, Guiqi 1/Shandong Poncirus trifoliata, and Guiqi 1/Longzhoutu lemon. The Pn variation of Jinbao Citrus reticulata,Daxinlayuegan,Huapi Fortunalla margarita and Shandong Poncirus trifoliate was due to non-stomatal limitation. The Pn variation of Guizhi No.1 Poncirus trifoliata and Longzhoutu lemon was caused by both stomatal limitation and non-stomatal limitation. ConclusionYoung Guiqi 1 navel orange trees that were grafted on Daxin Citrus reticulata performed well in every physiological way, so Daxin Citrus reticulata could be used as the rootstock for Guiqi 1 navel orange.