To explore the effect of volatile organic compounds (VOCs) on ozone (O3) formation during summertime when ozone (O3) pollution occurs frequently, the chemical composition characteristics of VOCs and its sources were studied, using high-resolution online monitoring data obtained in an urban site of Hohhot in the summer of 2021. In addition, the sensitivity of O3 pollution days and the control strategy of its precursors were further studied by observation-based model (OBM). Results showed that the averaged total mixing ratio of VOCs was 21.10±9.38 ppbv, with oxygenated volatile organic compounds (OVOCs) as the most abundant group (36.3%), followed by alkanes (23.8%), halogenated hydrocarbons (16.8%), alkynes(10.4%), aromatic hydrocarbons (6.6%), and alkenes (6.1%). Eight emission sources of VOCs, including restaurants emissions/biomass combustion, liquefied petroleum gas emissions, industrial emissions, gasoline vehicle exhaust, petrochemical sources, diesel vehicles, plant emissions and solvent use emissions, were resolved using PMF model, with contributions of 21.9%, 20.9%, 18.7%, 9.5%, 9.3%, 8.3%, 7.9% and 3.5%, respectively. According to the relative incremental reactivity (RIR) and EKMA analysis, O3 sensitivity was in the VOCs-limited regime during the O3 pollution days in Hohhot, with higher RIR values from alkenes, OVOCs and aromatic hydrocarbons. By simulating precursors reduction scenarios from the different VOCs sources resolved by PMF, the results showed that the reduction of VOCs from industrial related processes is most beneficial to the control of O3, while the reduction from traffic exhaust and liquefied petroleum gas emissions has little effect on the control of O3 and a risk of increasing O3.