This paper investigates the impact of photovoltaic generation system (PVGS) power variation on the transient response for a small off-shore island. The Chimei Island in Taiwan is elected for study. First, the power system network, diesel generation units, load and PVGS data are collected in detail. And the one-line diagram and the associated generator control model are set up in the Cyme Psaf program. After that, the transient stability analysis is executed with considering the tripping and power variation with various ramp rates of PVGS. The dynamic response of diesel generators and system frequency are examined carefully. It is therefore to obtain the maximum installation capacity of a single and total PVGS without violating the lowest operation frequency limitation.