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To investigate photochemical ozone (O 3 ) formation and provide localized control strategies, an intensive sampling of O 3 and its precursors (i.e. volatile organic compounds (VOCs) and nitrogen oxides (NO x = NO + NO 2 )) were conducted at an urban site in Leshan, Sichuan province during 4-13 August 2019. The mixing ratios of O 3 , total VOCs (TVOCs) and NO x were 40.0 ± 5.3, 22.5 ± 2.6 and 14.6 ± 3.8 ppbv, respectively (±95% confidence intervals). O 3 and its precursors existed a well negative correlation, indicating intensive local O 3 formation. To further explore the O 3 -precursors relationship and observation-oriented O 3 control strategies, a photochemical box model coupled with master chemical mechanism (PBM-MCM) was adapted. The relative incremental reactivity (RIR) calculated by model results showed that Leshan was in the VOCs-limited and O 3 production was most sensitive to alkenes. Moreover, O 3 isopleth diagram was drawn using the PBM-MCM simulation results and seven reduction scenarios were evaluated in Leshan. The reduction ratio of VOCs/NO x on 3:1 was proposed to be the best solution, which can be achieved effective reduction on local O 3 formation. At last, since VOCs were the key precursors of O 3 in Leshan, VOC sources and their potential contributions to O 3 formation were investigated by using the positive matrix factorization (PMF) model. Seven sources were identified, and traffic related emissions (including vehicle exhaust and gasoline evaporation, 29.9%) and fixed combustion (27.7%) had the large contribution to ambient VOCs. Among anthropogenic sources, fixed combustion and solvent usage in painting were the large contributors to O 3 formation, accounting for 30.9% and 18.3%, respectively, which should have high priorities on source reduction. This study provides scientific advices for future O 3 pollution control strategies in Leshan, which can be extended to other cities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)