Abstract: Unreduced gametes are the driving force for the polyploidization of plants in nature, and are also an important tool for ploidy breeding. The spontaneous formation of polyploid in plants by sexual polyploidization and asexual polyploidization is involved in nature. For the two ways to produce polyploid, sexual polyploidization is the more predominant way. In the present paper, mechanisms of 2n gamete occurrence in plants was summarized based on the analysis of cited references. Abnormal cytological phenomena, such as meiotic chromosome behaviour, meiotic microtubule and cytokinesis, meiosis Ⅰ to meiosis Ⅱ transition, and molecular regulator of 2n gamete formation was reviewed. Some problems for utilization of 2n gamete to produce polyploid in plants were also discussed. Detecting new genes related to 2n gamete formation based on combining the high-throughput sequencing, bioinformatics and multi-omics analysis, testing their biological function and elucidating the molecular mechanism of 2n gamete formation were pointed out to be hot research domains in the future. It might be one of the effective methods to solve the competition problem of haploid pollen during pollination and increase the triploid induction rate by accurately molecular design breeding combined with bioinformatic analysis and CRISPR-Cas9 mediated gene editing.