Through using the self-beat of fiber delay method, we measured the short-term frequency stability of Tm,Ho:YLF microchip laser cooled by liquid nitrogen. When the single longitudinal mode output laser power is 10 mW and the delayed fiber length is 100 m, 200 m, 300 m, 400 m and 500 m (delayed time ranging from 0.5～2.5 μs), respectively, the short-term frequency stability linearly increase from 1.5～4.75 kHz, and the linear slope coefficient is 1.48 kHz/μs. The oscilloscope′s Fourier integral time is about 40 ms, when the stability is measured. The laser can be the signal source for 2μm frequency stabilized laser.