Irrigation is a main agricultural management measure in arid regions. The area of irrigated farmland has reached 58.5 million hectares in China, and the area of water-saving irrigation has reached 29.0 million hectares with the development of sustainable agriculture. However, furrow irrigation is still widely used, especially in vegetable fields, which require multiple water sources. This results in the waste of water and issues relating to soil quality. Recent studies have demonstrated that irrigation can change the soil moisture conditions, and thus affect soil microbial activity. Soil microbial activity, a significant assessment index for soil quality, links the microbial community structure with ecosystem function. Therefore, determining microbial activity, both accurately and quickly, is important for the evaluation of soil microbial metabolism. Several approaches have been utilized to analyze soil microorganism activity in many studies. Soil enzyme activity and soil respiration are widely used; however, the results might lack accuracy due to certain limitations. Therefore, the objective of this study was to analyze the effects of different irrigation methods on soil microbial activity, which was assessed by soil enzyme activity, soil respiration, and microcalorimetric methods, based on a long-term irrigation experiment in Shenyang Agriculture University. Three irrigation methods were investigated, including drip irrigation (D), subsurface drip irrigation (S), and furrow irrigation (F) as a control. The results showed there was no significant difference in soil enzyme activity or soil respiration under different irrigation systems. Compared with conventional methods, the microcalorimetric method provided more useful information on changes in the soil microbial activity. The microcalorimetric method produced a power-time curve, which was a typical microbial growth curve. Based on the soil thermal dynamic index, changes in total heat, maximum thermal power, and growth rate under drip irrigation and furrow irrigation were negligible. No difference in microbial activity was observed between drip irrigation and furrow irrigation; however, activity was the lowest with subsurface drip irrigation. Therefore, drip irrigation with plastic was the method of water-saving irrigation most suitable for maintaining higher microbial activity in sustainable agriculture. Thus, the technology of subsurface drip irrigation should be further improved. Furthermore, the microcalorimetric method represents a novel way of detecting microbial activity, which was difficult to detect using traditional methods. As a consequence, the use of traditional methods to determinate soil microbial activity is limited, and the microcalorimetric method is highly sensitive for the determination of soil microorganism activity.