The laser properties of laser diode end-pumped Tm and Ho co-doped lithium yttrium fluoride (YLF) laser are studied. The experiment of Tm,Ho:YLF laser is conducted for different output couplings, and the optimum output coupler transmission is 2% when the crystal is kept at room temperature. The distribution of far field intensity is measured by pin-hole scanning, the output laser is proved to be operating in the TEM00 mode, and the relation between thermal focal length and pump power is obtained. To achieve single frequency operation, two solid, uncoated fused silica etalons are used. The laser threshold pump power is 250 mW, and the maximum continuous wave single frequency output power is 118 mW at the pump power of 2.8 W. The single frequency laser may be used as a seed laser for either a larger oscillator or an amplifier.