The distribution of population inversion has been obtained by solving the rate equations of a Tm and Ho codoped laser system. A giant pulse laser output of 88.4 mJ with pulse duration of 426 ns has been predicted at 0.1% duty cycle of LD pump source. In a 2 m ring resonator, the Tm, Ho:LuLF laser material has been side-pumped from three directions and Q-switched for acoustic-optic device. The slope efficiency is 6.36% in free running mode and 2.9% in Q-switching mode. When 3.25 J pump energy in 1 Hz repetition frequency is injected, it has been demonstrated that the laser pulse energy of 103.2 mJ with an optical-to-optical efficiency of 3.17% in the free running mode and 30.3 mJ with 0.93% optical-to-optical efficiency. When 3.5 J pump energy is injected, it has been obtained that the pulse energies of 129.3 mJ and 35.9 mJ in the two modes with optical-to-optical efficiencies of 3.69% and 1.02% respectively. The greatest dynamic to static ratio is 32.8%. The pulse duration is 417.2 ns when 3.25J pump energy is injected. If the ring resonator operates unidirectionally, the laser energy and the corresponding optical efficiency will be doubled, the result being in agreement with the theoretical analysis of rate equations.