Abstract: Diversity of solutions is one of the most important jobs of multi-objective optimization.Diversity includes the span and uniformity.In Multi-Objective Evolutionary Algorithms（MOEAs），population maintenance is used to realize the diversity.In this paper，a ∞-norm（infinite norm） based stepwise（INS） method is proposed to increase diversity of MOEAs.INS use ∞-norm as a measurement of diversity of individuals，and use stepwise method to wipe off individuals form population.Through experiments on 9 test problems，compared with two most popular MOEAs——NSGA-II and ε-MOEA，the experimental results demonstrate that INS can increase diversity of solutions obviously.