The petrochemical industry is a significant source of volatile organic compounds (VOCs) emissions, with critical implications for air quality and environmental health. However, the emission characteristics of intermediate-volatility and semivolatile organic compounds (I/SVOCs) and their role in secondary organic aerosol (SOA) formation remain unclear. In this study, the nonmethane organic gas (NMOG) emissions from various petrochemical processes were analyzed using two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-ToF-MS) and a novel semiquantitative methodology based on carbon number and functional group. Results showed significant variations in NMOG emission factors (EFs) and chemical speciation profiles, with the isophthalic acid production process being the highest (43.5 ± 30.9 g/t) and the phenol and acetone production process being the lowest (2.1 ± 0.7 g/t). Notably, I/SVOCs constituted 82.2% of emissions in the isophthalic acid production process. Oxygen-containing compounds were the dominant species in all tested processes, accounting for 55.0%-76.6% of I/SVOCs emissions. In addition, the contribution of I/SVOCs to SOA formation potential (SOAFP) ranged from 75.8% to 96.9%, with oxygenated aromatics being key contributors. This study highlights the significance of I/SVOCs emissions from the petrochemical industry and provides new insights into the direction of organic emission control at both the process and species levels.