Abstract: The acid-base indicator plant Hydrangea macrophylla was taken as the research object. A pot experiment was conducted, and four types of biochar, including Eucalyptus pyrolysis charcoal, Eucalyptus hydrothermal charcoal, camphor pyrolysis charcoal, and camphor hydrothermal charcoal. Three addition levels（0%, 0.2% and 1.0%） were set up to analyze the effects of biochar on the physical and chemical properties of green space soil, growth indicators and root morphological traits of Hydrangea macrophylla. The results showed that biochar treatment reduced the soil conductivity by 2.2% to 25.7%, the content of available phosphorus and available potassium significantly increased by 21.0% to 58.0% and 52.8% to 116.9%, and the urease activity increased by 5.8% to 57.3%, but it had a certain inhibitory effect on the activities of neutral phosphatase, amylase, and nitrate reductase. Adding 1.0% biochar significantly increased soil total organic carbon content（increased by 49.1% to 134.8%）.Different types of biochar had different effects on soil physical and chemical properties. Hydrothermal carbon was acidic and significantly reduced soil pH after application. The dissolved organic carbon content of Eucalyptus pyrolytic carbon, hydrothermal carbon, and 1.0% camphor hydrothermal carbon significantly increased by 31.2%, 30.6%, and 50.0%, respectively, while the organic matter content of Eucalyptus hydrothermal carbon added at two levels and 0.2% camphor pyrolysis carbon significantly increased by 18.3% to 57.6%. In addition, biochar significantly promoted the improvement of plant height, biomass, chlorophyll content, root morphology, and nutrient accumulation of Hydrangea macrophylla. Principal component analysis showed that the growth of Hydrangea macrophylla is closely related to soil environmental factors. Biochar application significantly increased the content of soil organic matter, organic carbon, inorganic nitrogen, and available nutrients, optimized soil enzyme activity and soil structure, thereby improved the photosynthetic capacity and nutrient accumulation effect of Hydrangea macrophylla. These promotion effects are significantly affected by biological raw materials, preparation methods and addition amounts.