Abstract: This paper analyzed the weak late stage signal of pulsed eddy current testing of the ferromagnetic materials briefly, and signal conditioning circuit was designed based on the analysis. Techniques of the impedance matching, electromagnetism shielding, grounding, floating empty DC voltage source and limited different pre-amplifying symmetrically are used and the SNR (Signal-to-Noise Rate) of signal conditioning system is improved effectively. The experiment results show that the design of weak signal conditioning circuit for pulsed eddy current improves the SNR and signal of several microvolts can be detected. Effective detection for the small corrosion of ferromagnetic materials in complicated electromagnetic environment is implemented.