In order to understand the transmission effect of the metal spring waveguide on terahertz wave, the transmission characteristics of terahertz wave by springs with different helix spacings have been studied experimentally. The experimental results show that when the pitch is larger as 3.5/4.4 mm (with wire diameter of 0.8 mm, outer diameter of 12 mm and length of 14 cm), the metal spring waveguide can propagate terahertz wave in a larger bandwidth with the additional ability of polarization maintaining. The terahertz transmission bandwidth of metal springs with pitch of 3.5/4.4 mm are both about 0.9 THz, and the lowest transmission loss are about 0.2 cm^-1 and 0.27 cm^-1 respectively at their peak frequencies. In addition, it has been proved that the terahertz mode was confined inside the air core rather than being guided by the metal helix. The above results are helpful for applications of the metal spring waveguide in the field of terahertz technology.