Three in-field investigations of dissolved organic matter (DOM) in the dry seasons from 2018 to 2020 were conducted in the Minjiang tidal reach. Three-dimensional fluorescence spectra of DOM of ebb and flow tides in different river sections were obtained. The correlation and principal component analysis (PCA) were used to assess the DOM fluorescence characteristic index. The results suggested that there were three types of fluorescence components in the research area including human-derived humic acid C1 (Ex/Em = 220–240 nm / 330–370 nm), terrestrial humic acid C2 (Ex/Em = 220–240 nm / 405–445 nm) and free amino acid and protein substance C3 (Ex/Em =255–285 nm / 310–360 nm). DOM in the upstream river reach was influenced by the reservoir operation and the human input. while in the middle river segment it was related to DOM component properties and the internal and external source input. The dilution and pollution block of sea water played important roles in the downstream estuary area. Besides, C1 was the characteristic pollutant in the research area. The FI, BIX and Fn(355) fluorescence characteristic index showed a decreasing trend year by year, while the HIX index decreased first and then increased. The FI and HIX index increased along the flow direction while BIX and Fn(355) decreased. Meanwhile, the exogenous and autogenic characteristics of the water close to the estuary were more obvious. Correlation analysis suggested that the DOM fluorescence characteristic index could be affected by the salinity and DO in the research area. Besides, dissolved total nitrogen and dissolved total phosphorus also had a great impact on the DOM fluorescence characteristic index when the upstream discharge flow was large. In addition, the PCA results indicated that the DOM fluorescence characteristics in 2020 were quite different from that in 2018 and 2019, which may also be related to the higher discharge from upstream.