The technique of interspecific hybridization between Ulva prolifera and Ulva linza was reported. Based on the phototactic response of zoids and the characteristics of life cycle, female gametophyte of U. prolifera and male gametophyte of U. linza was selected from the Ulva population. Mature thalli were induced to release gametes in a Petri dish under a unilateral light source. Gametes were purified at least twice according to their respective phototaxis. By homogeneous mixing and microscopic observation, we can find that female and male gametes swam rapidly to each other and joined to form zygotes. During the process of conjugation, the flagella of female and male gametes gradually disappeared, the motility decreased, and the shuttle-shaped gametes changed into round zygotes. After twice purification, the zygote can grow into the offspring of Ulva. The progeny of Ulva was examined by gel electrophoresis and molecular biology. Result showed that the hybrids had specific sequences of U. prolifera and U. linza on 5S rDNA spacer sequence. The successful hybridization of U. prolifera and U. linza was confirmed and the artificial hybridization technology of Ulva was established. This technology has not yet been reported in China before, and it can provide a technical demonstration for the future development of a variety of high-quality traits of Ulva strains. It can also provide scientific support for carrying out large-scale facility culture and obtaining stable and high-yield biomass of Ulva.