Chitin is the main component of fungal cell walls, which can be recognized by pattern recognition receptors (PRRs) as pathogen-associated molecular patterns (PAMP). Chitinase in filamentous fungi has been reported to degrade immunogenic chitin oligomers, thereby preventing chitin-induced immune activation. In this study, we identified the chitinase families in 10 fungal genomes. A total of 131 chitinase genes were identified. Among the chitinase families, 16 chitinase genes fromPuccinia striiformisf. sp.tritici(Pst) were identified, and the expression ofPstChia1was the highest duringPstinfection. Further studies indicated thatPstChia1is highly induced during the early stages of the interaction of wheat andPstand has chitinase enzyme activity. The silencing ofPstChia1revealed thatPstChia1limited the growth and reduced the virulence ofPst. The expression level of TaPR1 and TaPR2 was induced inPstChia1knockdown plants, suggesting thatPstChia1is involved in regulating wheat resistance toPst. Our data suggest thatPstChia1contributes to pathogenicity by interfering with plant immunity and regulating the growth ofPst.