Abstract: Genomic exchange and rearrangement of the amphidiploid species Cucumis hytivus and its effect on fertility of male gametophyte were cytologically studied through making slides.Cytolo-(gical)evidences for genomic exchange and rearrangement were found,such as"8"and"cross"configu-(rations)at prophase,chain and ring multivalents at metaphase Ⅰ,as well as various abnormal chro-(mosome)structure including chromosome bridges,lagging,genomic separation,micronuclei etc,which probably resulted in unequivalent distribution of genetic germplasm.Such an extensive geno-(mic)exchange and rearrangement led to 93% polyads and some abnormal tetrads.Abnormal micro-(spores)in polyads and microspores with unbalance germplasm could not develop into normal male gametophytes,which is responsible for the low fertility of male gametophyte in Cucumis hytivus.