Abstract: In view of the water-bearing composite stratum of Nanchang Metro Line 4, a muck improvement test has been conducted on saturated gravelly sand and moderately weathered argillaceous siltstone, and the appropriate modifier is selected and the performance test of the modifier is carried out. Based on the slump test, permeability test and direct shear test, the reasonable addition ratio of the modifier for saturated gravel sand and moderately weathered argillaceous siltstone are determined. The indoor muck test results are applied to the on-site muck improvement to verify the rationality of the indoor muck improvement test. The results show that the performance of the modifier meets the engineering requirements when the concentration of foam agent solution is 3% and the bentonite slurry ratio is 1∶8. For saturated gravelly sand muck, the proper addition method of modifier is that the ratio of foam to bentonite slurry is 4∶1, and the addition ratio is 5%~7%. For moderately weathered argillaceous siltstone, the proper addition method of modifier is that the ratio of foam to bentonite slurry is 1∶4, the addition ratio is 10.8%~12.6%, or the addition ratio of full bentonite slurry is 9.9%~12%.