Optically excited Lock-In thermography （OLT）which is an active thermography technique for NDT is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation.The development and application of OLT has been introduced to detect the defection of composite materials and structure in aerospace and automotive industry.In this study，the law of sine modulated lamp is used for active heat source to sample，and the thermal wave image sequences are collected with JADE MWIR 550 FPA infrared camera made in France Cedip Company.The special image sequence file formation is studied and analyzed.The digital filter algorithm and thermal wave signal single sequence Fourier transform algorithm are researched to obtain the phase angle image of thermal wave on the surface of sample.The program of IR Lock-In thermography is developed by Visual C++ language.The experimental results show that the lock-in thermography software system is reached to the Cedip IR Lock-In thermography technique advance level.