Abstract: According to the components of produced water in Chaheji oilfield, polyacrylamide and aluminum citrate, a kind of non- toxic environment- friendly crosslinker, are used to develop weak gel. A non - toxic environment -friendly weak gel system that is suitable for use in reservoirs of this oilfield is developed through optimizing concentrations of the main agent, crosslinker and additive. It is evaluated in laboratory in respects of the stability, sealing capability and enhanced oil recovery of the optimum formula. The problem of degradation of ferric ion is successfully solved.