The telemetry LIBS system including a coaxial Schwarzschild telescope is built to study the changes of the LIBS characteristic spectral line intensity, the relative standard deviation, the spectral similarity, and the plasma temperature, when the sample distance fluctuates at different guide positions, and to analyze the reasons for the changes of characteristic parameters based on the physical mechanism. The results show that the sample position fluctuation has a significant influence on the plasma temperature, the characteristic spectral line intensity, and the relative standard deviation, while the spectral similarity remains stable in a certain range. Under the condition that the spectrum satisfies a certain similarity, the tolerance of the sample position fluctuation increases linearly with sample distance. When the current system focus range is 1.9-4.1 m and the spectral similarity is 0.99, the range of the sample position fluctuation tolerance is 70-220 mm. The results are beneficial to the design of high-performance optical systems and provide theoretical references for qualitative and quantitative analysis of spectra.