In this paper, a common grounded Z-source dc-dc converter with high voltage gain is proposed for photovoltaic (PV) applications, which require a relatively high output-input voltage conversion ratio. Compared with the traditional Z-source dc-dc converter, the proposed converter, which employs a conventional Z-source network, can obtain higher voltage gain and provide the common ground for the input and output without any additional components, which results in low cost and small size. Moreover, the proposed converter features low voltage stresses of the switch and diodes. Therefore, the efficiency and reliability of the proposed converter can be improved.