Phenolic acids can have a significant allelopathic effect on plants, threaten plant growth and processing product quality. Trichosanthes kirilowii Maxim. was used as the study object. Through the indoor pot experiment, five different concentrations (0, 50, 100, 150, 200 mg/kg, designated as CK, T1, T2, T3, T4) of p-Hydroxybenzoic acid (pHBA), Benzoic acid (BA), and Cinnamic acid (CA) treatment solutions were added to the soil to study their effects on the physiology and soil characteristics of T. kirilowii, and the intensity and law of the allelopathic effect of phenolic acid were elucidated. The results showed that: (1) pHBA at T1 concentration can promote the elongation of the root system of T. kirilowii, and the growth rate of root fresh weight can reach 19.25%; BA affects the biomass accumulation of T. kirilowii, and at T4 concentration, it can inhibit the fresh weight and root fresh weight to 35.17% and 58.38% of the control group; under T4 concentration, CA have the most obvious inhibitory effect on plant height and root length, with the largest decrease of 66.19% and 63.13%. (2) Low concentration of pHBA could enhance root vigor, while high concentration inhibited it, the maximum inhibition rate was 33.55%; the allelopathic effect of BA on root vigor was positively correlated with the concentration, and the maximum inhibition rate was 47.41%. The effect of phenolic acid on transpiration rate and root vigor were slightly different, but the treatment of 150-200 mg/L showed obvious allelopathic inhibitory effect. (3) pHBA and CA improved SOD and POD activity and downregulated CAT activity; BA inhibited the activity of SOD, POD and CAT, which decreased by 47.42%, 59.07% and 45.43%, respectively. The degree of lipid peroxidation of the T. kirilowii membrane increased under all three phenolic acid stresses, but the damage was relieved as the stress time prolonged. (4) Phenolic acid stress significantly changed the soil microecology, and the activities of urease and invertase in the soil were more sensitive to it, and the microbial structure changed from "bacterial" to "fungal". The same concentration of benzoic acid had the deepest allelopathic effect on T. kirilowii cultivation, followed by p-hydroxybenzoic acid and the weakest was cinnamic acid. Therefore, reduction of the phenolic acid content in the soil is conducive to alleviate the allelopathic effect of the T. kirilowii, enhance the viability of the T. kirilowii, and thus improve the yield and quality of the T. kirilowii.