The voltage and current signals are transient signals with singularity and mutability when single-phase-to-earth fault occurs in high-voltage transmission line, of which the singular point and mutations parts contain rich fault information. However, wavelet analysis just has the nature of singularity detection and zoom properties, which is very effective in singularity analysis and singular points location. Based on the basic principle of wavelet analysis and signal singularity detection, simulation and detection of singularity of fault voltage and current signals in high voltage transmission line are made by db5 wavelet multi-scale comprehensive analysis method. The singularity detection and calculation program are accomplished in M-file form by programming in MATLAB, the simulation results show that db5 wavelet can detect the singularity of fault signal and determine the fault occurrence and end time fast and accurately. This method enhanced accuracy and reliability of single-phase-to-earth fault detection.