Low-cost, disposable, and high stretchability strain sensors attract considerable attention. In this paper, we conduct a numerical study to prove the concept of a low-cost and disposable microfluidic-based flexible sensor capable of detecting the arterial pulse waveform even if the sensor is under an axial strain of up to 160%. The strain sensor is comprised of an electrolyte-enabled long winding microchannel integrated with a pair of interconnects and silicone-based packaging. Two theoretical models and one finite element model(FEM) are established to evaluate the effect of the microchannel’s key design factors on the sensor performance. The key design factors of the microchannel, include the single winding width and length of the primary microchannel(PM), the width ratio ( secondary microchannel (SM) width to PM width), the number of the grid line, and the electrolyte material. Three models have a similar resistance change trend when under the same axial strain and same design parameters. However, the obtained resistance values from theoretical model 1 are much larger than those obtained from the FEM and theoretical model 2. The sensor is more sensitive when using ionic electrolytes as compared with liquid metal.