The preparation of thin lamellas by focused ion beam (FIB) for MEMS-based in situ TEM experiments is time consuming. Typically, the lamellas are of ~5μm*10μm and have a thickness less than 100nm. Here we demonstrate a fast lamellas’ preparation method using special fast cutting by FIB of samples prepared by conventional TEM sample preparation by argon ion milling or electrochemical polishing methods. This method has been applied successfully on various materials, such as ductile metallic alloy Ti₆₈Ta₂₇A_l5, brittle ceramics K_0.5Na_0.5NbO₃-6%LiNbO₃ and semiconductor Si. The thickness of the lamellas depends on the original TEM sample.