An out-crossing experiment bettween Populus alba L. × (Ulmus pumila L.+DEAD P. alba L. var. pyramidalis) was conducted. By using techniques of pollen inducement and puerile ovary culture, the out-crossing barrier was conquered, and hybrid seedling of P. alba × U. pumila were successfully produced. The hybrids of P. alba ×(U. pumila L.+DEAD P. alba L. var. pyramidalis) were named P. × alba L. 'yinyu'. Sterility usual occurred in hybridization of distant taxa. Sexual reproduction of interfamilial hybrids is concerned widely. Sexual reproduction of P. × alba L. 'yinyu' was studied in male and female from the following aspects: (1) The number of inflorescences, weight of pollen and vitality of pollen were recorded to evaluate sexual reproduction. P. × Liaonignica sp. Nov., P. alba L. var. pyramidalis and (P. simonii × P. euphratica) × P. nigra L. var. italica(Moench.) were used as controls. Pollen viability was detected by aceto carmine, culture medium and mating. The results indicated that the number of inflorescences of P. × alba L. 'yinyu' was the greatest, while the weight and vitality of pollen were the lowest among all tested samples. There were about 30% pollen tubes that were tortuose and forficate in culture medium. Colligating the results of dye and crossing, cross incompatibility was possible when P. × alba L. 'yinyu' was the male parent;(2) an pollination test of P. × alba L. 'yinyu' was conducted and P. × alba L. was used as a control. Female P. × alba L. 'yinyu' was pollinated, but showing difference affinities with different male parents. At last, the causes for pollen tube abnormality of P. × alba L. 'yinyu' were discussed. Some recommendations were also made on using P. × alba L. 'yinyu' as a parent.