Abstract: In recent years, many MSW landfills in China have adopted mining and screening for land reuse, pollution elimination, and incineration capacity optimization. Key parameters include the waste stock and the mass proportion of materials. This paper presents a method including small borehole exploration for waste distribution mapping, rotary drilling for in-situ density testing and sampling, and sieve analysis to quantify screened materials. Applied to a Shenzhen landfill, the method includes comparative analyses of appearance, physical composition, moisture content, particle size distribution, and density between samples from rotary drilling and small boreholes. Results demonstrate the superior representativeness of rotary drilling samples. Compared to rotary drilling, small borehole samples have 15% fewer coarse particles but 2.6%~13.7% more fine particles and 3.2%~21.9% more light materials. Depth analysis reveals decreasing characteristic particle sizes in rotary-drilled samples, and degraded particles mainly concentrate in 0.075~2 mm range, exhibiting a 7.6% increase in mass proportion. In-situ density of from rotary drilling increases from 6.09 to 12.53 kN/m³ with depth, while small borehole results are 10.7%~37.6% higher. The difference between the two methods decreases with depth. Based on the experimental results, the waste stock and quantities of screened materials are calculated. Compared to rotary drilling, the calculation error for small borehole samples ranges from 40.5% to 128.6%.