Abstract: Severe convective weather is frequently accompanied by abundant cloud-to-ground (CG) lightning flashes. Lightning location systems are capable of capturing lightning strike positions and supporting thunderstorm early warning services. To improve the application accuracy of monitoring data from the ADTD lightning location system and systematically evaluate the reliability of CG lightning monitoring data across Anhui Province, this study adopts CG return stroke data recorded by the Anhui ADTD lightning location system during 2014–2023. Reference observation points and typical lightning disaster cases are selected, and grid analysis, statistical analysis and consistency test methods are comprehensively utilized to evaluate the monitoring data quality of CG return strokes from two dimensions: positioning accuracy and lightning parameters (CG flash distribution and lightning current amplitude).The results are as follows.(1) Around the reference points, the positional error between high-value zones of CG return strokes and actual lightning locations ranges from 571 m to 1 442 m, exceeding the nominal systematic error of 500 m. Mountainous terrain causes prominent growth in positioning error. The contour distribution of CG return stroke counts around each reference point follows a consistent pattern: flash density is overestimated within the 0～1 km buffer, gradually converges to the regional average in the 1～2 km zone, and is markedly underestimated beyond 2 km; furthermore, the contour shapes basically coincide with mountain strike trends. (2) Statistics based on 10 representative lightning disaster cases reveal that the average positioning error over plain areas is 428 m, lower than the theoretical upper limit of systematic positioning error (500 m). Affected by terrain occlusion, the average positioning error in mountainous regions reaches 1070 m, which falls within the normal observational deviation range for complex terrain conditions. (3) The monthly and diurnal statistical characteristics of lightning activity are well consistent with the local evolutionary laws of severe convective climate. The cumulative probability distribution of lightning current amplitudes achieves a fitting consistency of 99.2% against the IEEE standard model, indicating an excellent matching degree with the standard model. The ADTD system presents high reliability in CG polarity identification and temporal consistency. Nevertheless, it exhibits a systematic overestimation bias for lightning current values within the 10～50 kA range.This study clarifies the error characteristics of lightning data under diverse terrain conditions, which can provide correction bases for lightning early warning, lightning disaster identification and lightning protection design in Anhui Province, and also offer a reference method for quality evaluation of lightning location systems in multi-terrain regions nationwide.