As a filler material in bioretention cells, loess has a good ability to remove nitrogen and phosphorus. However, its low permeability can easily trigger cell blockage. To improve permeability, the modification of loess has become important in the construction of bioretention cells. This study tested water-soluble epoxy resin-modified loess and investigated its feasibility as a filler for bioretention cells. Its purification performance under different rainfall conditions, including intensity and dry periods, was analyzed and compared with traditional sand bioretention cells both with and without a submerged zone. Epoxy-modified loess could be used as a bioretention cell filler, significantly increasing the permeability coefficient of the cell. Although modification with epoxy resin did not affect the crystal composition of the loess, the cross-linking reaction that occurred on its surface increased the C content, decreased the Si content, and made the texture rougher. When the amount of epoxy resin was 2.5 % (SZ25), the resulting loess met the permeability coefficient design requirements; its maximum adsorption capacity for ammonium-nitrogen was at least 1.92 times more than that of sand. For phosphate, the maximum adsorption capacity reached 5.17 mg/g. The average removal efficiencies of ammonium-nitrogen, nitrate-nitrogen, total nitrogen, and total phosphorus in the epoxy-modified loess bioretention cells were 91.67 %, −12.42 %, 39.91 %, and 91.97 %, respectively, 3.14 %, 28.91 %, 20.07 %, and 9.59 % higher than those in the sand bioretention cell. Microbiological analyses revealed that modified loess filler promoted the enrichment of denitrifying bacteria to a relative abundance 14.31 %–26.47 % higher than that in traditional sand filler. Based on the Functional Annotation of Prokaryotic Taxa analysis, the modified loess bioretention cell had stronger C and N cycling than that of the traditional sand bioretention cell, indicating that microbial metabolism and denitrification were stronger and nitrogen removal was improved.