The aerospace industry adopts aluminum alloy parts. Due to the demand for lightweight and other requirements in the aerospace industry, there is a high requirement for maintaining the strength of aluminum alloy parts. Therefore, the detection of structural material defects is particularly important. In this paper, a pulsed eddy current non-destructive testing (NDT) system based on tunnel magnetoresistance (TMR) sensor is designed. The relationship between aluminum alloy defect parameters and measured signal waveforms is studied. For the first time, finite element simulation software COMSOL was used to model and obtain simulation experimental data, which proved the feasibility of pulsed eddy current nondestructive testing in aluminum alloy materials. Secondly, the simulation results were used to guide the probe design, and designing a detection system, using the method of comparing the physical experiments results and simulation modeling analysis results. The experiment verifies the accuracy, reliability and feasibility of this detection system. Finally analyzed and discussed the non-destructive test results of defect width and defect depth. Established experimental basis for TMR sensor engineering application.