Small RNA molecules (small RNAs) have recently emerged as important regulators of gene expression at the post-transcriptional or translation level. Significant progress has recently been made in utilizing small RNAs to elucidate the molecular mechanisms regulating spermatogenesis. There are three major small RNAs: small interfering RNAs (siRNAs), microRNAs (miRNAs), and piwi-interacting RNAs (piRNAs). Small-RNAs have diverse biological functions in meiosis and spermatogenesis, In vitro or in vivo, use of siRNA to knockdown genes is a way to study the function of genes of interest in spermatogenesis. miRNA can be involved in the regulation of mitosis, meiosis, and postmeiosis in spermatogenesis. piRNAs are mainly involved in regulating the process of meiosis and postmeiosis, and repressing retrotransposon transposition in male germline cells. In this paper, we reviewed recent works on the synthesis, mechanism, function, and outlook of small RNAs.