To improve the water environment quality, the development of an effective photocatalyst for pollutant removal was considered a promising strategy. The aim of the development of a novel photocatalyst PNC is pursued by modifying copper-phenylacetylide (PhC2Cu) with nitrogen-doped carbon quantum dots (N-CDs). Leading to a remarkable improvement in its light absorption capability, electron transfer efficiency and photoelectrochemical properties. Importantly, PNC possesses the characteristic of straightforward synthesis and demonstrates remarkable performance in the photodegradation of 99.87% sulfamethoxazole (SMX) within just 15 min, with a 3.95-fold increase in the photocatalytic rate. Analysis of the active substances revealed that 1O2, O2·‐, and h+ are the generated active species by PNC. Active sites and degradation pathways of SMX were explored through density functional theory (DFT) calculations and intermediate analysis. Key evidence regarding the direction of electron transfer within the system was obtained through in-situ irradiated X-ray (ISI-XPS) techniques. This study deepened our understanding of the electron transfer characteristics of phenylacetylene copper and provided new insights for the modification of photocatalysts.