Screening magnesium （Mg）-efficient germplasm of oilseed rape （Brassica napus L.） will provide elite materials for studying molecular mechanism of Mg efficiency in Brassica napus.90 varieties of natural population of B. napus were used to examine 10 traits of the population including the weight of fresh biomass，the weight of dry biomass，the ratio of root to shoot and the accumulation of Mg under low and normal Mg treatments with the two-step screening method of nutrient solution culture at the stage of seedling to screen magnesium efficient varieties of B. napus and study the molecular mechanism of magnesium efficiency in B. napus.Correlation analysis，cluster analysis，and comprehensive evaluation analysis methods were used to comprehensively evaluate the magnesium efficiency in 90 varieties and screen magnesium efficient varieties.The results showed that there were significant differences in 10 traits of 90 varieties under 2 magnesium treatments，with a coefficient of variation ranging from 14.8% to 82.94%.The coefficient of low-Mg tolerance of 10 traits was significantly positively correlated.90 varieties were divided into four types including high-efficiency and low sensitivity type （14 varieties），high-efficiency and high sensitivity type （21 varieties），low efficiency and high sensitivity type （19 varieties），and low efficiency and low sensitivity type （36 varieties） based on the weight of dry biomass and the coefficient of magnesium efficiency under normal magnesium conditions as the main indexes for evaluation.The magnesium efficient varieties including W16 and W100 and magnesium inefficient varieties including W61 and W132 of B. napus were finally screened out through re-screening verification，which can provide materials for subsequent studies on the molecular mechanism of high magnesium efficiency in B. napus.