Abstract: Lignosulfonate is produced as a by-product of the pulp and paper industry by sulfate pulping process.It is abundant,biodegradable and cheap.Modified lignosulfonates(GCL2) has preferable performance in inhibition of corrosion and scale.In this paper,the effect of lignosulfonates on bacteria reproduction rate in recirculated cooling water has been studied by plate counting method.It was found that both wood-pulp and straw-pulp lignosulfonates would speed bacteria reproduction.Sugar in lignosulfonates is the main factor to speed bacteria reproduction.However,GCL2 would inhibit bacteria reproduction.Lignosulfonate oxidized by hydrogen peroxide would also inhibit bacteria reproduction.