The Tm³⁺ gain medium with high doping concentration can improve the quantum efficiency of the laser through the cross relaxation process, but it also increases the energy loss caused by energy up-conversion and limits the improvement of laser efficiency. The fluorescence characteristics and laser performance of Tm:SrF₂ crystal are studied. Under laser-diode (LD) end-pumping, a continuous-wave laser with a maximum output power of 2.99 W and a slope efficiency of up to 82.1% is realized. The pump threshold of the laser is 0.81 W, and the center wavelength is 1851 nm. Electro-optic Q-switching of the Tm:SrF₂ laser is demonstrated. At the repetition rate of 500 Hz, a maximum pulse energy of 1.02 mJ and a minimum pulse width of 45 ns are achieved, resulting in a peak power of 22.67 kW. The experimental results indicate that the Tm:SrF₂ laser based on LD pumping has very high efficiency and is expected to be an ideal pump source for optical parametric oscillators (OPOs) and optical parametric amplifiers (OPAs).