To reduce the temperature measurement error of distributed single-mode fiber temperature sensing systems, the paper proposes a temperature measurement method based on Golay-Simplex hybrid coding. First, four G codes are transformed into S codes to achieve 12-channel G-S hybrid coding modulation. Then, the output signals of the 12 channels are processed through S code decoding and G code decoding sequentially, employing cumulative averaging and wavelet transformation for temperature curve denoising. This verifies that the coding gain of the G-S hybrid coding is the product of the coding gains of the G and S codes. Comparative experimental results show that under conditions of 30 km fiber length, 50 ns pulse width, and 64-bit coding length, the amplitude fluctuation range of the anti-Stokes signal curve in the G-S hybrid coding temperature measurement system is smaller and has a higher signal-to-noise ratio across the fiber length compared to the Golay code-based temperature measurement system and the single-pulse temperature measurement system. The steady-state temperature measurement error of the G-S hybrid coding can be optimized from ±7.3°C in the single-pulse system to ±2.5°C, outperforming the measurement error of ±3.9°C in the distributed Raman fiber temperature measurement system based on Golay codes. Additionally, the spatial resolution can be maintained at 5 m, demonstrating the effectiveness of G-S hybrid coding for long-distance single-mode fiber temperature measurement, potentially providing effective technical solutions for the integrated perception of infrastructure conditions such as temperature changes due to leakage in hydraulic dams.