Helicon waves propagation and absorption of helical antenna is studied by solving Maxwell equations with finite element method and experimental parameters of H-1 stellarator. As axial length of helical antenna increases, total radiation resistance and radiation energy of the antenna increase as well. In H-1 plasma, helical antenna mainly excites m=±1 waves, and the m=-1 waves spread generally at the plasma boundary. Energy of the excited modes of full-wavelength helical antenna is mainly deposited at plasma boundary, which causes inhomogeneous radial energy absorption and heating. Excited waves of half-wavelength helical antenna penetrate deeply into the bulk plasma, which leads to relatively uniform radial energy absorption and heating.