Based on Ground Penetrating Radar technology, the paper examines the characteristics, electrical property features and morphological variations of common underground diseases in urban roads. It provides a comprehensive analysis of the radar spectrogram characteristics of various subsurface road diseases, which not only helps in their accurate identification, but also provides a basis for subsequent evaluation of road collapse. In addition, the paper integrates various factors, including underground diseases, into the evaluation of road collapse risk and establishes a "5-level" evaluation model. This leads to a unified research mechanism for detecting underground road diseases and assessing collapse risks. Taking a specific road project in Beijing as a case study, the paper uses the trapezoidal membership function to assign values to various indices that affect road collapse. Through fuzzy calculation, the collapse risk levels for road disease bodies 1#, 2#, 3# and 4# are determined to be level II (low risk), level III (medium risk), level IV (medium-high risk) and level V (high risk), respectively. It is recommended that for low-risk disease body 1#, routine patrols should be intensified; for moderate-risk disease bodies 2# and 3#, periodic inspections should be intensified; and for high-risk disease body 4#, immediate grouting reinforcement or excavation and backfilling should be undertaken.