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[Display omitted] • FTIR, mass reduction, and SEM reveal the effects of the digestion solution. • 30 % H 2 O 2 is the optimal digestion solution, which is the least harmful to MPs. • Elucidating the composition of MPs in landfills: PE, PP, PS, and PET dominate. The landfill is one of the most important sources of microplastics (MPs). The pretreatment method is a precondition of microplastics study for the presence of complex substances in landfills. Therefore, it is essential to examine the impact of different pretreatment methods on the microplastics detection. A literature review and a comparison experiment on digestion solutions were performed to establish a comprehensive identification method for MPs in landfills. When exposed to of 30 % H 2 O 2 , minimal mass reduction of PE, PP and PET were 4.00 %, 3.00 % and 3.00 % respectively, and the least surface damage was observed in MPs, while exhibiting the most optimal peak value for infrared spectral characteristics. It is demonstrated that the effect of 30 % H 2 O 2 dissolution was superior compared to 10 % KOH and 65 % HNO 3. The method was subsequently utilized to investigate the distribution of MPs in a landfill. The dominant MPs were polyethylene (PE, 18.56–23.91 %), polyethylene terephthalate (PET, 8.80–18.66 %), polystyrene (PS, 10.31–18.09 %), and polypropylene (PP, 11.60–14.91 %). The comprehensive identification method of "NaCl density separation + 30 % H 2 O 2 digestion + NaI density separation + sampling microscope + Mirco-FTIR" is suitable for the detection of MPs in landfills. [ABSTRACT FROM AUTHOR]