Due to the limitation of temporal and spatial factors, the succession of soil, microorganism and vegetation is usually studied by a spatial series representing the temporal series which is a kind of space-for-time substitution approaches, while the driving force of soil age is less studied. In this paper, four representative alluvial areas of the Yellow River Delta (the formation periods were 1904-1929, 1929-1934, 1964-1976 and 1976 to the present, respectively) were selected to design sampling routes from coastal areas to farmlands (1-40 km). The diversity of plants, bacteria and fungi, and the functional composition of microorganisms in terrestrial vegetation were studied by bio-diversity surveys, soil sampling, and high-throughput sequencing using the Illumina HiSeq platform. The results showed that with the increase of soil age, plant species richness and aboveground biomass increased significantly (P<0.05), and the distribution area of Imperata cylindrica (L.) Beauv. was advancing to the coast, which is a low-salinity indicator. In bacterial communities, the proportion of 3 phyla such as Acidobacteria, Nitrospirota, and Methylomirabilota increased significantly, while the proportion of other 12 phyla such as Bacteroidota, Gemmatimonadetes, and Patescibacteria decreased significantly (P<0.05). The functional pathway abundance of photosynthesis, and the basic life activities such as nucleotide metabolism and genetic information processing were enriched in the latest sector, while functional pathway abundance of aging,xenobiotics biodegradation and metabolism, and degradation of aromatic compounds were enriched in the earliest sector (LDA score>2, P<0.05). The relative abundance of groups of pathological nutrition increased significantly (P<0.05), such as Zoopagomycota. Soil age accounted for an unique portion to the variations of vegetation, bacterial, and fungal community composition (3.41%、2.61%、1.12%, respectively), which provided additional insights of the vegetation and microbial succession. Salt-tolerant bacteria, autotrophic bacteria, denitrifying bacteria, and desulfurizing bacteria were of higher richness in the later soil forming area, which have the potential to promote soil carbon and nitrogen accumulation, soil nutrient cycling, and soil availability at the early soil forming stage, and then affect plant succession. Soil age also drives the increasing ratio of groups that prefer high nutritional environment over pioneer groups and contributes to the differentiation trend of microbial niche. The study proves that soil age is an important and significant driving force for the change of vegetation and microbial community compositions in the Yellow River Delta and provides a scientific basis for improving the accuracy of assessment of the vegetation and microbial succession in coastal ecosystem.