Objective: To study the effect of different patterns of Q-switched ruby laser on UVB-induced skin pigmentation in guinea pigs. Methods: Ten guinea pigs were included in study, and the back of each guinea pig was divided into 4 groups, that is control group receiving UVB irradiation but no laser treatment, low-dose group, high-dose group and fractional group, UVB irradiation was used to induce pigmentation of the skin, low-dose, high-dose and fractional areas receiving UVB irradiation followed by the treatment with laser at an energy density of 1.5, 6.0 and 3.0 J/cm2 for 4 times, twice, and once. Respectively, with all interval of 1 week, Photograph, Fontana-Masson, and scanning electron microscopy were performed to observe melanin granules and melanosomes in the skin tissue from guinea pigs before the initial laser treatment at once, 2 weeks after the final laser treatment. Results: The best response were observed in the low-dose areas and fractional group and there was a complete clearance of hyperpigmentation in two groups, which maintained 8 weeks without recurrence, while different degrees of skin pigmentation recurred in the high-dose group. Moreover, low-dose group, high-dose group and fractional group showed a significantly lower melanin granules and melanosome, compared with the control group (P<0.05). Conclusion: Q-switched ruby laser is effective to skin pigmentation in guinea pigs, it is better on fractional of Q-switched ruby laser.