Global climate change and population growth exacerbate various biotic (e.g., infection of pathogens) and abiotic (e.g., drought, salinity, high temperature, etc.) stress in agricultural production, which impede plant growth, development and productivity by affecting plant morphology, physiological and biochemical characteristics as well as metabolic functions. Consequently, this affects crop yield and quality and seriously threatens agricultural sustainability. With the vigorous development of modern agriculture, beneficial microorganisms have attracted much attention due to their ability to improve soil quality and fertility, stress tolerance in crops, and their yield and quality. Besides, the proper use of microbial inoculum in agricultural production can achieve the effects of reducing the amounts of agrochemicals, reducing production costs, improving the quality of agricultural products, and protecting the ecological environment, which is also in line with the agricultural production goal of harmonious coexistence between humans and nature. In this review, the types and application effects of plant growth-promoting bacteria (PGPB) were briefly summarized, with emphasis on the analysis of PGPB's ability to produce phytohormone, fix nitrogen, facilitate the absorption and utilization of nutrients (phosphate and potassium solubilization and siderophore production), alleviate biotic and abiotic stress, regulate plant root architecture and rhizosphere microbial community structure. Moreover, the frontier science and technology of PGPB inoculum preparation and application methods in modern agriculture in recent years were systematically explored, and the application prospect and research direction of PGPB in future agricultural production were further discussed.