Multiple factors in the river-lake connected system can affect the transport and transformation of arsenic (As) in sediments. In this study, As source and sink characteristics under phosphorus (P) competition in sediments from river (R), lake (L) and lake-centre (LC) of river-lake connected system were analyzed, and the As release regionality and continuity were also discussed. The study showed that the ORP of the sediments at each site was negative with a mean value of -151 mV. The sediments in the R region were weakly acidic and those in the LC region were weakly alkaline. The R region had relatively high EAsC