The p-GaN/i-In x Ga 1-x N/n-GaN double-heterostructure photovoltaic (PV) cells have been fabricated and the theoretical photovoltaic properties were also calculated in this work. From theoretical simulation, higher efficiency can be obtained in GaN/InGaN double-heterostructure photovoltaic cells with higher In composition in i-InGaN intrinsic layer. GaN/InGaN double-heterostructure photovoltaic cells with In compositions of 10, 12, and 14 were fabricated and characterized for demonstrating with the simulated results. The corresponding photoelectrical conversion efficiency of fabricated GaN/InGaN photovoltaic cells with In compositions of 10, 12, and 14 is 0.51, 0.53, and 0.32 under standard AM 1.5G measurement condition, respectively. GaN/InGaN photovoltaic cells with In composition of 10 showed high open-circuit voltage (V oc) of 2.07 V and fill factor (F.F.) of 80.67. The decrease of V oc and FF was observed as In composition increasing from 10 to 14. For comparing with the fabricated GaN/InGaN photovoltaic cells, theoretical conversion efficiency of GaN/InGaN photovoltaic cells with In compositions of 10, 12, and 14, is 1.80, 2.04, and 2.27, respectively. The difference of GaN/InGaN photovoltaic properties between theoretical simulation and experimental measurement could be attributed to the inferior quality of InGaN epilayer and GaN/InGaN interface generated as the increase of In composition.