Peroxyacetyl nitrate (PAN) is a typical secondary product of VOCs and NO_x photochemical reaction,and a better indicator of photochemical smog than O₃.The ambient levels of PAN in Jinhua from June to October,2019 were measured by online instrument,and the PAN variation and correlated influencing factors,as well as one typical photochemical pollution episode were analyzed.The results showed that the average volume fraction of PAN was 0.656×10^-9,with maximum value recorded as 4.348×10^-9.Daily averaged PAN volume fractions were ranged from 0.130×10^-9 to 2.203×10^-9.The diurnal variation of PAN was a double-peak pattern in September and a single-peak one in other months.The ambient PAN level in summer was generally lower than that in autumn due to the meteorological influences.During the typical pollution episode from September 27th to September 30th,the hourly mean PAN volume fraction was 2.8 times of that during the whole observation period,and the pollution was dominated by local accumulation.The difference of precursor concentration and removal mechanism were important factors affecting the correlation between PAN and O₃,in addition,the ratio of NO/NO₂ was an important factor affecting the PAN formation rate,and the peak PAN values appeared during time with low ratio of NO/NO₂.Propane,ethane and m,p-xylene were the most important VOCs precursors of PAN.