The invention discloses a gear with a novel tooth profile curve. A tooth profile curve at the tooth top of the gear is in a convex shape. A tooth profile curve at the tooth root of the gear is in a concave shape. A meshed tooth pair of a gear pair is in convex-concave arc meshing. In a coordinate system O-xy with the gear center as an original point, through a gear parameter and tooth profile curve parameter equation, the tooth profile curve is obtained, the tooth profile curve is subjected to symmetry and rotation transformation, then the end face profile of the gear is obtained, and the gear pair formed by gears is in conjugation and in convex-concave arc meshing. The gear can be used in tooth profile design in large-load gear transmission, the bearing capacity of the gear is greatly increased compared with an involute, when a rack tool or hobbing is used for machining, machining tool design is simple, and only one tool needs to be machined. The gear is also used in design of a small-tooth-number gear pair with a small tooth number (z is smaller than or equal to 6), and accordingly the bearing capacity is improved.