A method for breeding a small-grain male-sterile rice line and a simple method for producing a hybrid rice seed are provided. The method for breeding the small-grain sterile rice line includes the following steps: crossing a female parent C815S with a male parent Qigui B to obtain a hybrid seed F1; planting the F1 and crossing the F1 with a female parent H155S to obtain a crossed hybrid seed F1′; planting the crossed hybrid seed F1′ to obtain a F2′ generation; planting an individual plant with ideal plant type, strong tillering, plant dwarf and small grain type from the F2′ generation and a F3′ generation, and then directional breeding more than two generations to obtain a seed with more than F5′ generation as the small-grain sterile rice line.