Helical antenna with small reflection surface

The invention discloses a helical antenna with a small reflection surface, aiming at improving the helical antenna gain, enlarging the launching coverage range of a launcher and meeting the long-distance communication requirement of a tire pressure monitor system (TPMS). The helical antenna comprises a body and the reflection surface, wherein the body has a spiral structure formed by winding a metal wire or a metal tube, and is a normal mode helical antenna; and the reflection surface is arranged under the body and is connected with a negative pole or a ground wire of a feeding point of the body. The reflection surface meets the condition that (D0-D)/2 is more than or equal to A-x and less than or equal to A, wherein D is the screw diameter of the body, D0 is the diameter of the reflection surface, A and x are constants, x is more than 0 and less than A, A is more than x and less than or equal to 0.01 lambda, and lambda is the wavelength of a signal transmitted by the launcher within the free space.