The entire process of microcrack nucleation in a TiAl-Cr-V alloy with different microstructures is observed in situ by a scanning electronic microscope (SEM) during compressive deformation. The main results are summarized as follows: (1) In the fully lamellar microstructure, the microcracks nucleate mainly at the lamellar grain boundaries between soft-orientation and hard-orientation grains. (2) In the Widmanstatten structure, the microcracks distribute mainly at the intersection between two Widmanstatten plates. (3) In the duplex structure, the microcracks form at the lamella/ lamella and lamella/gamma boundaries. (4) In the nearly gamma structure, microcracks nucleate at gamma/gamma grain boundaries.