Off-line membrane filtration, solvent extraction and continuous spectral analysis were mainly used to monitor and analyze the atmospheric particulate matter in Xi’an city, China, for a continuous year from December 25, 2016 to December 26, 2017. Atmospheric PM2.5 samples were collected by quartz fiber filter firstly, and then water-soluble organic carbon (WSOC) and methanol-soluble organic carbon (MSOC) were ultrasonically extracted by ultra-pure water and methanol respectivelly. Finally, UV-vis absorption spectrum was used to obtain the light absorption characteristics of the samples. By analyzing the absorption contribution of water soluble brown carbon (BrC) and methanol soluble BrC in winter and summer in Xi′an at 365 nm, it was found that the absorption efficiency of methanol extraction was higher than that of water extraction in winter and summer, and the annual mean of methanol-soluble organic carbon mass absorption efficiency (MAE(MSOC)) ((1.60±0.67) m2·g－1) is 1.17 times of that of water-soluble organic carbon mass absorption efficiency (MAE(WSOC)) ((0.90±0.47) m2·g－1), indicating that there is a large amount of organics with stronger light absorption in MSOC. In winter, MAE(WSOC) and MAE(MSOC) are (2.05±0.86) m2·g－1 and (1.53±0.36) m2·g－1 respectivelly, while MAE(WSOC) and MAE(MSOC) in summer are (1.06±0.24)) m2·g－1 and (0.51±0.17) m2·g－1 respectivelly, which shows that MAE in winter is higher than that in summer. And the calculated E250/E265 value of WSOC in winter (5.25) is lower than that in summer (5.58), which may be caused by winter coal-fired heating emissions. The correlation analysis between WSOC and the six meteorological elements was carried out, and it is shown that WSOC is correlated with PM2.5 (R2 = 0.6417) and PM10 (R2 = 0.4035), while there is no obvious correlation between WSOC and O3 (R2 = 0.0682), indicating that the source of the secondary photochemical reaction accounts for a small proportion.