A comparative study was made on the nutrient content in rhizosphere soil and the microflora in rhizosphere soil and on rhizoplane of healthy and red-leaf diseased Salvia miltiorrhiza plants, aimed to approach the microecological mechanisms of redleaf disease occurrence in S. miltiorrhiza. The N, P, K, and Mn contents in the diseased plant leaves were significantly lower than those in the healthy plant leaves (P＜0.05). No significant difference was observed in the available P content in the rhizosphere soils of diseased and healthy S. miltiorrhiza, but the available N and K contents were significantly higher (P＜0.05) in the rhizosphere soil of diseased S. miltiorrhiza. These results indicated that the red-leaf disease occurrence in S. miltiorrhiza was related to plant P deficiency, but the lack of P in the plants was not caused by the insufficient soil P supply. As compared with those in healthy S. miltiorrhiza rhizosphere, the bacterial number in diseased S. miltiorrhiza rhizosphere soil decreased by 41.3%, while the fungal and actinomycetes numbers increased by 156.6% and 189.5% (P＜0.05), respectively. Similar variations in the numbers of bacteria, fungi, and actinomycetes were observed on diseased S. miltiorrhiza rhizoplane. In the rhizosphere soil and on the rhizoplane of diseased S. miltiorrhiza, the predominant microbial species that might be harmful included six fungi (Fusarium solani, Myrothecium roridum, F. tricinctum, Aspergillus calidoustus, F. oxysporum, and Dothideomycetes sp.), four actinomycetes (Streptomyces lateritius, Lentzea waywayandensis, S. stelliscabiei and S. collinus), and two bacteria (Bacillus aryabhattai and Piscinibacter aquaticus). These predominant soil microbes likely caused plant P deficiency via negatively affecting the growth of roots and their absorption of soil nutrients. It was suggested that the red-leaf disease occurrence in S. miltiorrhiza was closely related to the plant P deficiency caused by the abnormality of soil microflora in the rhizosphere soil and on the rhizoplane of S. miltiorrhiza.