To investigate the seasonal dynamics and influencing factors of soil stoichiometric characteristics and microbial elements use efficiency in the rhizosphere and bulk soils, the rhizosphere and bulk soils of Robinia pseudoacacia plantations in three seasons (Spring, Summer, and Autumn) were selected as the study objects on the Loess Plateau. Soil physicochemical properties, microbial biomass, and enzyme activity were determined, and stoichiometric imbalance, vector characteristics, and element use efficiency were calculated. Combined with Partial least squares path model analysis of various related environmental factors, this study investigates the seasonal variation mechanism of microbial element utilization efficiency in rhizosphere and bulk soils. The results showed that the seasonal dynamics significantly influenced stoichiometric imbalance, with both rhizosphere and bulk soils C ∶ N imbalance showing an increase trend followed by decrease across seasons, reaching its maximum value in summer (0.91, 3.22). While C ∶ P and N ∶ P imbalances exhibited the opposite pattern. The VL of rhizosphere and bulk soils are highest in summer, while VA are greater than 45° in spring and autumn, and less than 45° in summer. Changes in VL and VA indicated that soil microorganisms in both rhizosphere and bulk soils experienced stronger carbon and nitrogen limitations in summer, and stronger phosphorus limitation in spring and autumn. The seasonal dynamics have a significant impact on the utilization efficiency of microbial elements, with carbon utilization efficiency being the lowest in summer, with an average of about 0.33, and nitrogen and phosphorus utilization efficiency being the highest in summer. This indicates that rhizosphere soils microorganisms have a stronger contribution to carbon fixation in spring and autumn, while bulk soils microorganisms have a stronger contribution to nitrogen and phosphorus fixation in summer. The results of the partial least squares path model indicate that the factors affecting soil element utilization efficiency include stoichiometric imbalance and resource limitations. Both rhizosphere and bulk soils microorganisms indirectly affect element utilization efficiency through vector features and extracellular enzyme activities, while stoichiometric imbalance in bulk soils had direct effect on microbial elemental use efficiency. Soil microorganisms adapt to the environment by adjusting enzyme investments in different restricted nutrients, in order to alleviate resource limitations caused by stoichiometric imbalances and thus affect seasonal differences in element utilization efficiency. The results contribute to an in-depth understanding of the nutrient utilization mechanisms of rhizosphere and bulk soils microorganisms in plantation forests, and provide a theoretical basis for the management of plantation forests in ecologically fragile areas.