Abstract: The detection of nanoplastics (NPs, <1 000 nm) in complex matrices faces technical bottlenecks in separation, identification, and quantification. This study summarized the applicable scenarios and limitations of different technologies in terms of sample pretreatment and identification analysis. The results indicated that a multistage digestion approach, combining hydrogen peroxide pretreatment with enzymatic digestion followed by density-gradient ultracentrifugation, enables efficient purification while preserving the integrity of plastic particles. Tandem mass spectrometry provides high sensitivity and a wide detection range, and can simultaneously achieve identification and determination of polymers. Furthermore, pyrolysis–gas chromatography–mass spectrometry is suitable for the identification and determination of NPs in various environmental samples. Single-particle inductively coupled plasma mass spectrometry analyzes NPs <50 nm through metal-element labeling, with accuracy >84.4%. This study analyzed the applicability and limitations of known advanced technologies, providing a theoretical foundation and technical support for the accurate identification and risk assessment of NPs in complex environmental matrices.