Q-switched Er:YAG laser and free-running Er:YAG laser are used to study the laser ablation for the fresh porcine thighbones tissue in vitro. The ablation threshold range of the Q-switched laser and the free-running laser are 1.80~2.40 J/cm2 and 3.46~5.00 J/cm2, respectively. The results indicates that the ablation threshold of the Q-switched laser is lower. The fresh porcine thighbones tissue in vitro is irradiated by the two laser modes under the conditions of repetitive rate of 3 Hz, pulse energy of 200 mJ, and pulse number of 15 times. In addition, the morphologic changes of the tissue crater are observed by a scanning electron microscope (SEM). The morphology and the microstructure of the incision surface of the tissue ablated by the two laser modes are compared. Meanwhile, in the process of laser ablation, temperature distribution of the irradiation region with the two lasers for the tissue is measured by thermal infrared imager. Results show that after laser ablation for the tissue by the Q-switched laser, the lancing is smooth and the thermal damage for the surrounding histocyte is slight. Thus, in the process of the laser ablation for the porcine thighbones tissue in vitro, the Q-switched laser has a significant advantage.