This study aims to explore the temporal and spatial variations of soil total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), and the relationships between C/N, C/P and TOC, TN, and TP in bioretention tanks. Two bioretention tanks (tank No. 1: depth of 0~20 cm was vacant aquifer layer, 20~90cm, filled with planting soil, 90~105 cm, filled with gravel; tank No. 3: 0~20 cm was aquifer layer, 20~50 cm, filled with planting soil, 50~90 cm, filled with blast furnace slag and sand; 90~105cm, filled with gravel) were used in simulation stormwater runoff purification experiments to collect planting soil samples at intervals of one hour before inflow and 24 hours after the end of inflow. The results revealed that soil TN, TP, and TOC in 2 bioretention tanks were mainly concentrated at 10~30 cm in soil. The contents of TN and TP varied from 0.32 g kg^-1 to 0.50 g kg^-1 and from 0.83 g kg^-1 to 1.35 g kg^-1 within the investigated zone, respectively. Soil TN content in the 2 bioretention tanks before the inflow was slightly greater than after the inflow, but the opposite was true for TP, as it was less before the inflow than after. The potential of TN and TP fixation in No. 1 was higher than that in No, 3 within the upper 30 cm depth, which were related to the infiltration rate of underlying fillers (the underlying fillers of No. 1 is planting soil, and which is the blast furnace slag and sand in No. 3). The TOC content in the 2 bioretention tanks varied from 4.24 g kg^-1 to 8.97 g kg^-1, and the average contents decreased with the increasing depths. The C/N and C/P were positively correlated with TOC, while they were negatively correlated with TN and TP contents, which showed that soil C/N and C/P were mainly controlled by TOC in soil. The conclusions can provide references for the design and operation evaluation of bioretention facilities.