Spatial resolution and signal-to-noise ratio are difficult to be improved at the same time due to the small signal and big noise in Rayleigh Brillouin optical time domain analysis (BOTDA) system. A technique of pulse coding is introduced into Rayleigh BOTDA system, and then the signal-to-noise ratio and Brillouin frequency shift measurement accuracy of the system can be improved effectively without decreasing spatial resolution. The principle of the temperature sensing system based on Rayleigh BOTDA is analyzed. The characteristic of Golay complementary sequence is introduced and the expressions of the signal-to-noise ratio between single pulse system and coded pulse system are achieved. Rayleigh BOTDA temperature sensing systems of single pulse and coded pulse are constructed. The temperature sensing characteristic of single pulse system and the spatial resolution and the accuracy of temperature measurement of coded pulse system are measured. The experimental results show that the Brillouin frequency shift obtained by the Rayleigh BOTDA system has a linear relationship with temperature, and the temperature coefficient is (1.109±0.010) MHz·℃ -1. The spatial resolution of 1 m and temperature accuracy of 1.39 ℃ are obtained on the heated section of 1.77 km fiber when Golay code is 64 bit and the pulse width is 10 ns.