Abstract: ObjectiveGenesis and development of megaspore and microspore in Calotropis gigantea(Linn.) W. T. Aition was explored to provide basic information in cultivation science and botany , and lay a foundation for genetic breed-ing research and variety improvement. MethodFlower buds of C. gigantea at different developmental stages during full-bloom stage were gathered. Paraffin section was adopted to observe the genesis and development characteristics of megas-pore and microspore. ResultThere was corresponding relation between developmental stages of megaspore and microspore and flower organs morphology characteristics. The genesis and development of stamen was earlier than that of pistil. In contrast with dispersed microspores in ordinary plants, microspores of C. gigantea were conglutinated into block structure. Development of microspore mother cell was of successive type. There were three to four layers of tapetum cells , which were glandular tapetum. Tapetum cell wall degraded at uninucleate stage and autolyzed after maturity of pollen. Development of embryo sac was of polygonum type with amphitropous ovule and no integument. Tetrad formed linear arrangement. Mature embryo sac has secondary polar nucleus. ConclusionThere is close relation between development of megaspore and mi-crospore , female and male gametophytes development and flower organs morphology. The low seed setting rate is not caused by female abortion or male abortion.