In this study, 56 kinds of halogenated flame retardants (HFRs) were measured in surface sediments (n=28) collected from Dianshan Lake, Shanghai. Their temporal-spatial distribution characteristics, pollution sources, and potential ecological risks were explored by means of the variance analysis, principal component analysis (PCA), and risk quotient (RQ). Rapid industrialization and urbanization in Shanghai have caused obvious accumulations of HFRs in surface sediments from Dianshan Lake. The concentration of alternative brominated flame retardants (∑22 ABFRs, 21.418ng/g) was greater about two times than that of legacy brominated flame retardants (∑23 PBDEs, 10.344ng/g). BDE209 (7.890ng/g), decabromodiphenylethane (DBDPE, 17.990ng/g) and dechlorane plus (∑Syn+Anti DP, 1.176ng/g) were the predominant congeners. The higher concentration values of three kinds of HFRs mainly existed at the southwest of Dianshan Lake, probably attributed to the intensive human activities including daily living and industrial production. There were no significantly seasonal differences for the three kinds of HFRs (P>0.05). The PCA results revealed that the HFRs in surface sediments primarily derived from the use of commercial deca-BDE, penta-BDE, octa-BDE, and their alternative products, as well as the emission from related products containing ABFRs. The ecological risk assessment showed that penta-BDE, BDE209, DBDPE, 1,2-bis-(2,4,6-tribromophenoxy)ethane (BTBPE), and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB) in most of sediments posed medium risks to the sediment dwelling organisms, and BDE209 with high risk in certain sampling site. Therefore, the environmental supervision of these HFRs should be strengthened in the future. © 2024 Chinese Society for Environmental Sciences. All rights reserved.