Abstract: In recent years, numerous MSW landfills in China have been mining, screening, and reutilization to achieve land reuse, pollution sources elimination, and redundant incineration capacity satisfaction. This paper proposes a set of investigation methods based on large-diameter rotary drilling sampling and indoor screening tests to evaluate the amount of waste and various screened materials. These methods were applied to a landfill in Shenzhen to investigate the landfill. A comparative analysis was conducted on the appearance, physical composition, moisture content, particle size distribution, and density of samples obtained by large-diameter rotary drilling and traditional small boreholes. The results show that samples obtained by large-diameter rotary drilling represent the characteristics of landfill waste better. Compared to rotary drilling, coarse particles in small borehole samples are 15% smaller, while fine particles and light materials are 2.6%~13.7% and 3.2%~21.9% larger. As the depth increases, the characteristic particle size of rotary drilling samples gradually decreases. Small particles mainly concentrated in the 0.075~2mm size group, increasing by 7.6% in mass proportion. The density of waste obtained by rotary drilling increases from 6.09 to 12.53 kN/m³ with burial depth, which is 10.7%~37.6% lower than that obtained by small borehole sampling. The difference between the two methods gradually decreasing with depth. Based on the results, the amount of MSW and various screened materials in a landfill in Shenzhen were calculated. The calculation error of small boreholes compared to rotary drilling is about 40.5%~128.6%.