Plant phenology is very sensitive to climate change. However, the interactive effects of different climatic variables on plant phenology are still unclear. Thus, taking Quercus mongolica as the research object, we studied the interactive effects of different warming and changing photoperiod (control treatment (CK), 1.5℃ warming, 2.0℃ warming; different photoperiods (10 h, 14 h, and 18 h); CK, 1.5℃ warming×18 h, 1.5℃ warming×10 h, 2.0℃ warming×18 h, 2.0℃ warming×10 h) on the spring phenology of Quercus mongolica seedlings based on the experimental data of large artificial climate simulation chamber in the context of global warming. The results are as follows:(1) Under the same water condition, different warming had different effects on the spring phenology of Quercus mongolica seedlings. The 1.5℃ warming promoted the spring phenology, including bud swelling (BS), bud opening (BO), first full leaf (F1), and 50% leaves unfolded (LU) stages. The influence of 2.0℃ warming on different spring phenology was different. 2.0℃ warming promoted the release of bud dormancy and leaf BO, but inhibited the leaf extension. (2) Under the same water condition, the effect of different photoperiods on the spring phenology of Quercus mongolica seedlings was different. The long photoperiod had the greatest influence on the 50% LU stage, while the short photoperiod had the greatest influence on the BS stage, but they all showed negative effects. (3) Under the same water condition, prolonging photoperiod under warming treatments was helpful to promote the spring phenology of Quercus mongolica seedlings, including the BO, F1 and 50% LU stages. While shortening of photoperiod under warming treatments inhibited the spring phenology of Quercus mongolica seedlings, including the BS, F1 and 50% LU stages. (4) There was a significant correlation between spring phenological changes of Quercus mongolica seedlings and previous climate stress, implying that the previous climatic variables should be the significantly controlling factors to phenological changes. The results could enrich the cognition of the interactive effects of multiple climatic variables in Quercus mongolica phenology, and are helpful to promote plant phenology simulation.