The invention discloses a design method for the shape of a helicopter tail beam, belongs to shape design technology of the helicopter theory and relates to the shape design method for the tail beam of a single rotor wing helicopter with a tail rotor, and the tail beam is integrally designed and easy for maintenance. The design method is characterized in that the shape of the helicopter tail beam is composed of a rear helicopter body transitional molded surface, a tail beam integrated control molded surface and a tail beam rear end face, wherein the tail beam integrated molded surface is formed by integrally designing a tail transmission shaft fairing and a tail beam structural covering; the rear helicopter body transitional molded surface is a transitional surface formed by connecting the tail beam integrated control molded surface and the rear helicopter body; the tail beam rear end face is a rear structural surface of the tail beam. According to the design method disclosed by the invention, due to the adoption of the integrated design of the tail transmission shaft fairing and the tail beam structural covering, the inside of the tail beam is enabled to form sufficiently big loading volume and the tail beam has the advantages of light weight, capability of being maintained and the like. In addition, the streamline shape transitional design of the tail beam and the helicopter body is realized, so that the appearance is attractive and elegant; besides, the surface of the helicopter body is enabled to maintain good pneumatic performance.