Lakes are important in terrestrial carbon cycling. Source and optical composition of chromophoric dissolved organic matter (CDOM) in oligotrophic and deep lakes can display distinct properties, because of deep light penetration and long water residence time in these lakes. In this study, the optical properties and spatiotemporal distributions of CDOM were analyzed through monthly field investigation in 2017 in Lake Fuxian, an oligotrophic deep lake in Yunnan Province, China. The results showed that the average value of a(254) was 3.47±0.57 m^-1, with the range of 1.82-5.22 m^-1, indicating that CDOM abundance in the lake was relatively low compared with other mesotrophic and eutrophic lakes. Moreover, parallel factor analysis was performed to assess CDOM composition from excitation-emission matrix spectra and four components were identified:two tyrosine-like components (C1 and C3), one tryptophan-like component (C2) and one humic-like component (C4). The percentage of fluorescent intensity of C1+C3 was 65.81%±15.38%, and the proportion of C2+C4 was 34.19%±15.38%. The fluorescence index (FI), humification index (HIX) and biological/autochthonous index (BIX) was 1.73±0.14, 1.02±0.37 and 1.23±0.27, respectively. These results demonstrated that the CDOM was primarily originated from endogenous microbes in this lake. The average values of a(254) in spring (March-May), summer (June-August), autumn (September-November) and winter (January, February and December) were 3.20±0.47, 3.76±0.64, 3.67±0.50 and 3.23±0.38 m^-1 respectively, with significantly higher values in summer and autumn than those in winter and spring. The abundance and spatial distributions of autochthonous and allochthonous CDOM exhibited seasonal heterogeneity, which might be correlated with land-use pattern, input of terrestrial materials, rainfall, water temperature and irradiance.