Quantifying the multifunctionality of natural forest ecosystem, and analyzing the trade-off and synergy between different functions and driving factors are of great significance for natural forest protection and restoration. The data of the study include permanent sample plots from the eighth national forest inventory in Jilin Province, soil data and climate data of natural mixed broad-leaved forest. To characterize the ecosystem multifunctionality, eight ecosystem functions were selected, including soil conservation, water conservation, carbon storage, climate regulation, soil fertility maintenance, biodiversity, productivity and wood production. The Ecosystem Multifunctional Index is calculated by using standardization of a maximum observed value in the average method. The results show that:(1) There are trade-offs, synergies and neutrals among the eight functions, but the synergy is dominant. In addition to the trade-off between biodiversity and climate regulation, it has a synergy with other functions. The synergy between carbon storage and wood production is the strongest(r=0.960, P<0.01). The trade-off between climate regulation and water conservation is the strongest(r=-0.934, P<0.01). (2) The multifunctional index of natural mixed broad-leaved forest in Jilin Province is between 0.31 and 0.89, and biodiversity and climate regulation are the leading functions. (3) The coefficient of determination by structural equation model of multifunctionality and driving factors is 0.795. The total path coefficients of the driving factors of multifunctionality are as follows:stand density index (0.752) > average age (0.375) > annual precipitation (0.365) > tree species richness (0.101) > soil pH (0.064) > structural diversity (-0.037) > annual average temperature (-0.105), and stand density is the most important driving factor. The results are of great significance to understand the formation and management of natural mixed broad-leaved forest multifunctionality.