A gas burner (1), which is used in domestic cooking appliances; consists of a pool (1.1), a flame crown (1.2) and a lid (1.3); has a high thermal efficiency; and easy to assemble/disassemble. In the said burner (1), the ports (1.2.2), from which the flames exit, are positioned in such a way that the angle B is between 10° and 30°. Additionally, the angle A of the upper surface (1.2.9) of the flame crown and the lower surfaces (1.2.2.1) of the port is inclined in such a way that, it is between 15° and 35°. Thus, the flame coming out of the burner ports (1.2.2) is elevated and in this way, the thermal efficiency of the burner (1) is increased as the flames get closer to the object to be heated. Besides that, at the inner part of the burner (1) pool (1.1), a vertical assembly channel (1.1.2) is provided and at the lower part of the flame crown (1.2), a vertical assembly extension (1.2.3) is provided. By engaging the said vertical assembly extension (1.2.3) to the assembly channel (1.1.2), the assembly of the pool (1.1) with the flame crown (1.2) is realized easily with one possibility, mis-assembly by the user is prevented and thus, the possible dangers which might occur in the prior art are prevented beforehand.