Physical characteristics of stem are closely relative to the crop lodging. Increase of stem strength is conducive to resolve the problem of lodging. Three soybean cultivars with different shade tolerance were planted under maize-soybean intercropping and soybean monocropping, respectively. Physiological and biochemical indices including cellulose, soluble sugar, sucrose, starch contents and enzyme activity were investigated to assess the snapping resistance and lodging resistance of the stems of soybean seedling, and snapping- and lodging-resistance indices were calculated for further verification. Furthermore, relationship analyses between these factors and the lodging of inter-cropped soybean showed that the intercropping soybean lodged seriously, the snapping resistance, lodging resistance index, contents of cellulose, soluble sugar, sucrose, starch and activities of the related enzymes were significantly lower than monocropping soybean at seedling stage. The three soybean cultivars showed different phenotypes in intercropping condition. The snapping-resistant Nandou12 with strong shade-tolerant traits was the most lodging-resistant phenotype, and it also harbored high contents of cellulose, soluble sugar, sucrose, starch and active enzymes. The lodging resistance index, cellulose content of the stems of intercropped soybean seedling were significantly positively correlated with the snapping resistance, and were significantly negatively correlated with the actual lodging percentage. The activities of sucrose phosphate synthase (SPS) , sucrose synthase (SS) and neutral invertase (NI) were positively correlated with sucrose is content, but not the acid invertase (AI). The activities of SPS, NI and SS were positively correlated with cellulose content, but not Al. In a word, the high activities of SPS and SS in the soybean stem were the enzymatic basis to maintain relatively higher cellulose and sucrose content, which is conducive to improve the stem-sfrength and enhance the lodging resistance ability in intercropping condition. Effects of different light conditions on cellulose metabolic mechanism of soybean seedling stems, lodging resistant characteristics of soybean seedlings studied in the corn-soybean intercropping system provided a basis for screening more shade-tolerant soybean variety.