A method for knitting a three-dimensional shoe blank by a flat knitting machine, comprising: providing at least a yarn to knit and form a heel and lateral portion, after forming the heel and lateral portion, a plurality of lateral live stitches are preserved on needle beds at first pending selvage edges (10a, 10b) along two sides of an end edge of the heel and lateral portion; continuing knitting and forming a rear sole portion from a predetermined number of stitches along the center of the end edge of the heel and lateral portion, wherein when the number of stitches reaches a predetermined number on first connecting selvage edges (20a, 20b) at the two sides of the rear sole portion while knitting the rear sole portion, the flat knitting machine moves transversely from side to side to sequentially knit live stitches at the edge of the rear sole portion together with the lateral live stitches on the needle bed (FB, BB) respectively, so that the heel and lateral portion is combined with the rear sole portion to form a three-dimensional rear shoe part; continuing knitting and forming a front sole portion from the rear sole portion, wherein the knitting is gradually narrowed at two sides when knitting the front sole portion, and a plurality of latitudinal live stitches are preserved on the needle bed (FB, BB) at second pending selvage edges (30a, 30b) along the two sides of the front sole portion; continuing knitting and forming a toe cap portion from the front sole portion, and when the knitting of the toe cap portion reaches two sides at second connecting selvage edges (40a, 40b), sequentially knit live stitches on the two sides of the toe cap portion together with the latitudinal live stitches on the needle bed (FB, BB) respectively to form a three-dimensional front shoe part in a bag shape; and continuing knitting and forming a tongue portion from the toe cap portion. providing at least a yarn to knit and form a heel and lateral portion, after forming the heel and lateral portion, a plurality of lateral live stitches are preserved on needle beds at first pending selvage edges (10a, 10b) along two sides of an end edge of the heel and lateral portion; continuing knitting and forming a rear sole portion from a predetermined number of stitches along the center of the end edge of the heel and lateral portion, wherein when the number of stitches reaches a predetermined number on first connecting selvage edges (20a, 20b) at the two sides of the rear sole portion while knitting the rear sole portion, the flat knitting machine moves transversely from side to side to sequentially knit live stitches at the edge of the rear sole portion together with the lateral live stitches on the needle bed (FB, BB) respectively, so that the heel and lateral portion is combined with the rear sole portion to form a three-dimensional rear shoe part; continuing knitting and forming a front sole portion from the rear sole portion, wherein the knitting is gradually narrowed at two sides when knitting the front sole portion, and a plurality of latitudinal live stitches are preserved on the needle bed (FB, BB) at second pending selvage edges (30a, 30b) along the two sides of the front sole portion; continuing knitting and forming a toe cap portion from the front sole portion, and when the knitting of the toe cap portion reaches two sides at second connecting selvage edges (40a, 40b), sequentially knit live stitches on the two sides of the toe cap portion together with the latitudinal live stitches on the needle bed (FB, BB) respectively to form a three-dimensional front shoe part in a bag shape; and continuing knitting and forming a tongue portion from the toe cap portion.