Spatial resolution is an important parameter of Brillouin optical time domain analysis (BOTDA) sensing system,which depends on the width of pump pulse light. To improve the spatial resolution of BOTDA system,spiral coiled optical fiber method is used without changing the width of pump pulse light. Brillouin scatter sensing principle is analyzed. The influence on improving spatial resolution in actual measurement process using coiled optical fiber is analyzed on theory. In the experiment,the width of pump pulse light is 10 ns,the sampling interval of BOTDA system is 0.4 m. The spiral coiled optical fiber with 1 m length is used to monitor the axial temperature distribution of 0.5 m pipeline and monitoring spatial resolution is 0.5 m. Analysis results show that spiral coiled optical fiber is more available to improve the spatial resolution in monitoring pipeline temperature field.