The metabolic characteristics of soil microbial carbon source are important indexes to evaluate the change of soil quality. Based on the scientific observation and experiment station of agricultural environment and efficient water use for crops in Shouyang County, Jinzhong City, eastern Shanxi Province, this study used Biolog-ECO microplate technology to explore the effects of film mulching (FM) and no film mulching (LD) on the carbon source metabolism of soil microorganisms in different soil depths (0-10 cm, 10-20 cm and 20-30 cm) in 3 key growth stages of dry-farming spring corn. The results show that:1) the FM measures can significantly increase the utilization ability of soil microorganisms to carbon sources, significantly improve the richness index of soil microorganisms, but reduce the evenness index of soil microorganisms. 2) In 0-10 cm and 10-20 cm soil layers, the utilization of microbial carbon sources in FM and LD treatments were higher in filling period, while in 20-30 cm soil layer, the harvest period was higher, and the differences were mainly reflected in 3 types of carbon sources:carbonaceous water, carboxylic acids and amino acids. 3) The utilization capacity of microbial carbon source in 0-10 cm soil layer of FM treatment was significantly higher than that of LD treatment at jointing stage and filling stage; However, in the 0-10 cm soil layer at harvest time, the oppositely is true, showing that the utilization capacity of soil microbial carbon source under LD treatment is significantly higher than that under FM treatment. 4) In addition, Pearson correlation analysis showed that under FM treatment in this study, the utilization ability of soil microorganisms to 2 kinds of carbon sources, namely, carbohydrate carbon source and carboxylic carbon source, had a good correlation with soil organic carbon(SOC) and total nitrogen(TN) content, showing a positive correlation; The utilization ability of amino acid carbon sources is mainly related to soil water content, pH, SOC, NH₄⁺-N and NO₃^--N content. Under LD treatment, the utilization ability of carbon sources such as carbonaceous water, carboxylic acids and amino acids by soil microorganisms had a good correlation with TN content in soil, and showing a positive correlation.