The invention discloses a haynaldia villosa agglutinin receptor-like kinase gene, its expression vector and an application thereof, and belongs to the field of gene engineering. According to the invention, cDNA sequence of Hv-LecRK is SEQ ID NO.1 and amino acid sequence coded by Hv-LecRK is SEQ ID NO.2. The gene is derived from Haynaldia villosa L.(2n=2x=14, genome VV), and can interact with powdery mildew resistance-related gene Hv-CMPG. Expression of the gene is enhanced when the gene is induced by powdery mildew in the powdery mildew resistant diploid haynaldia villosa. Through transient expression, the gene is transformed to a susceptible wheat variety Yangmai 158. It shows through results that overexpression of the Hv-LecRK gene can reduce haustorium index of Yangmai 158. Thus, the Hv-LecRK is expected to be used in genetic engineering breeding. By introducing the Hv-LecRK into a wheat variety susceptible to powdery mildew, powdery mildew resistance of wheat is expected to be raised.