The pollution of surface runoff has become an important part of urban non-point source pollution. The dissolved organic matter (DOM) is the main component of organic pollutants. Because DOM contains a large number of unsaturated structures and functional groups, including hydroxyl, carboxyl, carbonyl, amine groups, etc., these structures are easy to complex with heavy metals in runoff, changing the form of heavy metals, affecting the migration and transformation and its bio-availability. Based on surface runoff as the research object in Beijing, this paper studies the characteristics of DOM in different underlying surface in different functional areas in winter as well as summer and its mechanism of complexing with heavy metals,study the different components of DOM in runoff from summer and combination mechanism with heavy metal Cu²⁺, Pb²⁺, Zn²⁺ by fluorescence quenching titration experiments. Research results show that PARAFAC will decompose the samples into 2 types and 6 different components, including one types of humus, one types of protein-like; The quenching rate of fluorescence intensity by Cu²⁺, Pb²⁺ and protein material is stronger than those with humus, while Zn is exactly opposite; Two-dimensional correlation synchronous spectrum reveal the facts that the sensitivity of DOM to heavy metal Cu²⁺, Pb²⁺, Zn²⁺ decreases successively, and the asynchronous spectrum illustrate that Cu²⁺,Pb²⁺ will react with the protein -like spectral band between 270-300nm firstly, Zn will prior to react with the humus spectral band near 330 nm.