Enhance sensitivity of the terahertz (THz) wave sensor by the THz wave control characteristic based on artificial electromagnetic meta-materials, is a hot spot in current research. The performance of split ring resonators (SRRs) THz sensor on Mylar substrate is numerical simulated with COMSOL Multiphysics software in this paper. The two key characteristic parameters of the THz sensor are analyzed with COMSOL Multiphysics software, which are the thickness of the Mylar substrate and the gap width of the gold SRRs. By comparing the relationship between different parameters and the corresponding resonance frequency curve, the optimal parameters of the THz sensor are obtained which are 10 microns for the Mylar substrate thickness, 2 microns for the gap width of gold SRRs. Then the optimized THz sensor model is used to test the different thickness and relative dielectric constant material with the COMSOL Multiphysics software. The results show that the resonant frequency (f0) move to lower frequency with the increase of the relative dielectric constant of tested materials, and has a good linear relationship between the f0 and the relative dielectric constant of tested materials. While the f0 also move to lower frequency as the thickness of tested materials are increase, but when the thickness are more than 5 microns, the resonance peak stay at near 1.997 THz. They are show that the SRRs THz sensor on flexible substrate has high measurement precision, sensitivity, and reliability when the tested materials are common metal, semiconductor and medium layer which layer thickness is less than 5 microns, and the relative dielectric constant for the range of 1-4 by the linear relationship between the resonance frequency and the different parameters of tested materials, as well as it can provide theory references for actual testing of such terahertz sensors.