A novel series of samples Sn 1−x Ga x P 2 O 7 (x=0.00, 0.01, 0.03, 0.06, 0.09, 0.12, 0.15) are synthesized by solid state reaction. XRD patterns indicate that the samples of x=0.00−0.09 exhibit a single cubic phase structure, and the doping limit of Ga 3+ in Sn 1−x Ga x P 2 O 7 is x=0.09. The protonic and oxide-ionic conduction in Sn 1−x Ga x P 2 O 7 are investigated using some electrochemical methods at intermediate temperatures (323–523K). It is found that the samples exhibit appreciable protonic conduction in hydrogen atmosphere, and a mixed conduction of oxide-ion and electron hole in dry oxygen-containing atmosphere. The highest conductivities are observed for the sample of x=0.09 to be 4.6×10 −2 Scm −1 in wet H 2 and 2.9×10 −2 Scm −1 in dry air at 448K, respectively. The H 2 /air fuel cell using x=0.09 as electrolyte (thickness: 1.45mm) generates a maximum power density of 19.2mWcm −2 at 423K and 22.1mWcm −2 at 448K, respectively.