<p>To quantitatively evaluate high-grade encrustation in double-J (DJ) stents and identify its risk factors in patients undergoing ureteroscopy and laser lithotripsy. This retrospective study analyzed 56 encrusted DJ stents from patients post-ureteroscopy and laser lithotripsy. Encrustation severity was classified using the FECal (Forgotten, Encrusted, Calcified) grading system. Clinical, laboratory, and stent characteristic data were collected. Composition and extent of encrustation were assessed via inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM). Logistic regression analysis was performed to identify risk factors for high-grade encrustation. Among the 56 encrusted stents, FECal grades were: I (<i>n</i> = 23), II (<i>n</i> = 12), III (<i>n</i> = 18), IV (<i>n</i> = 1), and V (<i>n</i> = 2). High-grade encrustation (Grades III-V) was significantly associated with female gender (66.7% vs. 34.3%, <i>p</i> = 0.019), urological stone history (33.3% vs. 5.7%, <i>p</i> = 0.010), and indwelling time &gt; 4 weeks (52.4% vs. 25.7%, <i>p</i> = 0.044). Multivariate analysis confirmed indwelling time &gt; 4 weeks as an independent risk factor (OR = 3.9, <i>p</i> = 0.049). Calcium oxalate was the main component, with encrustation initiating on black-ring areas and near side holes and gradually extending to cross-sectional regions. The FECal grading system effectively reflects encrustation severity. Indwelling time &gt; 4 weeks is a key predictor of high-grade encrustation. Side holes and the black marker ring are high-risk areas for mineral deposition. Developing stents with improved biocompatibility and anti-encrustation coatings could mitigate encrustation risks.</p>