According?to?the?monitoring?data?in?Xicheng?canal,?Baiqugang?river,?Zhangjiagang?river?and?Heng?river?of?Jiangyin?city,?the?relationship?between?chlorophyll?a?(Chl.a)?concentrations?and?physio-chemical?factors?was?investigated.?Besides,?the?factors?that?are?significantly?correlated?with?Chl.a?using?the?methods?of?multiple?linear?stepwise?regressions?were?selected.?The?results?indicated?that?there?was?an?obvious?temporal?and?spatial?variation?of?Chl.a.?Correlation?analysis?showed?that?the?significantly?important?environmental?factors?which?affect?Chl.a?were?not?always?the?same?in?four?investigated?rivers.?In?general,?the?main?environmental?factors?affecting?Chl.a?were?water?temperature?and?exogenous?inputs?for?the?first?three?rivers,?plus?phosphorus?and?ammonia?for?Heng?river.