【Objective】This study investigates soil degradation and impediment layer evolution in the Northeast China black soil region through micro-morphological analysis. To overcome insufficient impregnation during unsaturated polyester resin (UPR) consolidation of compacted soil samples, 【Method】we developed bulk density-specific for six soil samples and texture-specific protocols for four soil types. Methodological innovations include acetone-modified UPR formulations and a three-criterion evaluation system (sectioning integrity, surface durability, pore filling). 【Conclusion】Results showed bulk density-dependent optimization: bulk density >1.7 g/cm3 sample required 90% acetone-diluted 191# UPR, bulk density 1.70~1.50 g/cm3 sample required 80% acetone-diluted 191# UPR, bulk density 1.40~1.50 g/cm3 sample required 90% acetone-diluted 191# UPR, bulk density 1.30~1.40 g/cm3 sample required 80% acetone-diluted 191# UPR, bulk density 1.20~1.30 g/cm3 sample required neat 191# UPR, and bulk density <1.20 g/cm3 sample required 80% acetone-diluted 191# UPR. Texture-dependent optimization: silt needed neat or 90% acetone-196# UPR, silty loam required 80% or 90% acetone-diluted 191# UPR, loam performed best with 80% acetone-diluted 191# UPR, and sandy loam used neat or 80% acetone-191# UPR. 【Conclusion】This decision framework enhances sample preparation efficiency by 40% (from 6.2±0.5 to 3.7±0.3 hours) and improves lamella quality scores by 25% (Cohen's d=1.2). The findings provide methodology for high-quality soil micro-morphology analysis, critically advancing mechanistic understanding of impediment layer development in mollisols.