Biogas slurry is a cheap source of plant nutrients and can offer extra benefits to soil fertility and fruit quality. However, its current utilization mode and low content of active ingredients limit its further development. In this paper, a one-growing-season field study was conducted to assess the effects of concentrated biogas slurry on soil property, tomato fruit quality, and composition of microflora in both nonrhizosphere and rhizosphere soils. The results showed that application of concentrated slurry could bring significant changes to tomato cultivation, including increases in organic matter, available N, P, and K, total N and P, electrical conductivity, and fruit contents of amino acids, protein, soluble sugar, beta-carotene, tannins, and vitamin C, together with the R/S ratios and the culturable counts of bacteria, actinomycetes, and fungi in soils. It was concluded that the application is a practicable means in tomato production and will better service the-is area of sustainable agriculture.