We have developed an laser ablation system with an automatic focusing (AF) and robotic scanning mechanism for precision malignant gliomas resection in neurosurgery. A 5-aminolevulinic acid (5-ALA)-induced fluorescence based intra-operative tumor diagnosis technique has been incorporated into the robotic laser ablation system. The system enables an intra-operative identification of the position of a tumor with fluorescence illuminated by a laser excitation. The AF and robotic scanning mechanism assists in tracking the surface of the malignant brain tumors, and provides position information for both laser scanning in 5-ALA fluorescence identification and laser ablation in tumor resection. Experimental results showed the automatic focus device had a precision of 0.5 mm and the mechanism could track the brain surface with a movement caused by pulsation and respiration.