Haploids are individuals with gametophytic chromosome numbers. Homozygous doubled haploids can be quickly gained by genome doubling. Haploids and doubled haploids play an important role on crop breeding, mutant screening, gene functional analysis, cytological studies, construction of genetic population and so on, and have been a research hotspot of plants in recent years. In this review, we summarize the production means, identification, the genetic mechanism and the applications of haploids and doubled haploids. We hope to provide a reference for study and application of haploids and doubled haploids.