According to the extended nonlinear Schrdinger equation including quintic nonlinearity in optical fibers, modulation instability (MI) based generation of high-repetition-rate optical pulse trains is numerically demonstrated by using the optical wave with its phase perturbed by Gaussian-typed continuous spectrum instead of conventional monochromatic one. The results show that, the pulse trains can also be generated due to MI effect like the conventional case. However, being different from the conventional case, the generated pulse trains here consist of limited number of pulses which are generally not equal in width, intensity, and interval. And the pulse number increases with the propagation distance. Moreover, when the other parameters are the same, the positive quintic nonlinearity can make the pulse width and interval shorten, which means that the positive quintic nonlinearity is beneficial to generate higher repetition rate pulse trains. While the negative one takes the opposite. The numerically calculated chirps developed during the generation process of pulse trains indicate that, both the chirps and their variations with the distance are highly nonmonotonic, and the quintic nonlinearity will change both the chirp range and the chirp amount.