A motor rotor with a permanent magnet tangentially embedded, comprising a rotor body, which has a plurality of permanent magnet slots arranged along a circumferential direction and a polygonal slot located between two adjacent permanent magnet slots, the polygonal slot being symmetrical with respect to a magnetic pole centerline between the two adjacent permanent magnets, wherein the polygonal slot comprises: a first slot side, arranged at a first end of the polygonal slot along the circumferential direction of the rotor body, and having a first endpoint A away from a center of the rotor body and a second endpoint B adjacent to the center of the rotor body, in a section perpendicular to a central axis of the rotor body; and a second slot side, arranged at a second end of the polygonal slot along the circumferential direction of the rotor body, and having a third endpoint C away from the center of the rotor body and a fourth endpoint D adjacent to the center of the rotor body, in the section perpendicular to the central axis of the rotor body, wherein the second endpoint B and the fourth endpoint D are distinct separate points, characterized in that along a direction away from the center of the rotor body, a spacing between the first slot side and the second slot side is increasing, a distance from a connecting line between the first endpoint A and the third endpoint C to the center of the rotor body is denoted by h1, a radius of the rotor body is denoted by R, and h1 and R satisfy: 0.96≤h1/R≤0.99; and a connecting line between the first endpoint A and the center of the rotor body is a first connecting line, a connecting line between the third endpoint C and the center of the rotor body is a second connecting line, and an included angle Φ between the first connecting line and the second connecting line satisfies: 3.7°≤Φ≤5.6°. wherein the polygonal slot comprises: a first slot side, arranged at a first end of the polygonal slot along the circumferential direction of the rotor body, and having a first endpoint A away from a center of the rotor body and a second endpoint B adjacent to the center of the rotor body, in a section perpendicular to a central axis of the rotor body; and a second slot side, arranged at a second end of the polygonal slot along the circumferential direction of the rotor body, and having a third endpoint C away from the center of the rotor body and a fourth endpoint D adjacent to the center of the rotor body, in the section perpendicular to the central axis of the rotor body, wherein the second endpoint B and the fourth endpoint D are distinct separate points, characterized in that along a direction away from the center of the rotor body, a spacing between the first slot side and the second slot side is increasing, a distance from a connecting line between the first endpoint A and the third endpoint C to the center of the rotor body is denoted by h1, a radius of the rotor body is denoted by R, and h1 and R satisfy: 0.96≤h1/R≤0.99; and a connecting line between the first endpoint A and the center of the rotor body is a first connecting line, a connecting line between the third endpoint C and the center of the rotor body is a second connecting line, and an included angle Φ between the first connecting line and the second connecting line satisfies: 3.7°≤Φ≤5.6°.