To address the limitations of existing optical dust detection methods, which are susceptible to environmental factors and lack precision, a novel method and system for detecting dust accumulation on photovoltaic modules has been developed. This system integrates temperature and humidity data into its detection algorithm to mitigate environmental influences on measurement accuracy. The optical path structure is optimized, and incident light intensity data are collected to compensate for variations in the light signals received by photosensitive elements. A synchronous demodulation circuit is designed to eliminate background light interference, thereby enhancing detection accuracy. Furthermore, a new calibration method reduces both calibration complexity and cost while further improving precision. Test results demonstrate that this system achieves high accuracy and robust anti-interference performance, with a maximum deviation of 1.67% under outdoor high-temperature conditions, outperforming traditional equipment by 0.55%. Additionally, the stability in low-temperature and high-humidity environments has been enhanced by approximately 2.9%, enabling longterm monitoring capabilities, meeting the operational requirements of photovoltaic power stations.