Dissolved　organic　matter（DOM）is　important　for　determining　the　speciation，environmental　behavior，and　ecological　risk　of　lead（Pb）in　the　aquatic　environment.　However，the　underlying　mechanism　for　the　complexation　of　leaf　litter　DOM　with　Pb（II）remains　unclear.　Photochemical　and　microbial　degradation　are　two　key　processes　in　determining　the　level，composition，and　reactivity　of　dissolved　organic　matter（DOM）.　This　study　examined　the　effects　of　photo-　and　microbial　degradation　on　the　transformation　of　DOM　released　from　reed　leaf　litter　and　the　interaction　between　DOM　and　Pb（II），by　laboratory　incubation，spectroscopic　characterization，and　fluorescence　quenching　titration.　Four　humic-like　components（C1~C4）and　one　protein-like　component（C5）were　identified　with　fluorescence　excitation-emission　matrices-parallel　factor　analysis.　Humic-like　components　were　more　susceptible　to　photo-degradation，while　the　protein-like　component　was　preferentially　utilized　by　microbes.　Photo-degradation　played　a　dominant　role　in　the　short-term　photo-microbial　degradation.　For　the　original　leaf　litter　DOM，Pb（II）was　mainly　complexed　with　humic-like　components（C1，C2，and　C4），while　C3　showed　significant　fluorescence　quenching　only　after　photo-microbial　degradation.　The　protein-like　C5　complexed　with　Pb（II）after　photo-　and　photo-microbial　degradation.　The　conditional　stability　constant　logKM　of　humic-like　C1　increased　after　photo-degradation　and　decreased　after　photo-microbial　degradation.　The　logKM　of　C2　and　C4　both　increased　after　degradation.　The　complexation　fraction　f　and　the　complexing　capacity　Fmax·f　of　C1，C2，and　C4　reduced　after　all　degradation，which　was　more　significant　after　photo-degradation　than　after　microbial　degradation.　These　results　demonstrated　that　the　changes　of　DOM　abundance，composition，and　structure　by　photo-　and　microbial　degradation　would　strongly　affect　its　complexation　stability　and　complexation　capacity　with　metal　ions.　©　2022　Science　Press.　All　rights　reserved.