We have developed a new, to the best of our knowledge, femtosecond laser spatiotemporal imaging technique, named asynchronous wide-field transient absorption microscopy (AWTAM), which does not require phase synchronization between an optical chopper and a complementary metal–oxide–semiconductor (CMOS) camera. By presenting a theoretical scheme, an image reconstruction algorithm, and experimentally imaging the photocarrier diffusion process in a 2D layered semiconductor, our technique has been comprehensively demonstrated. Our technique is widely applicable for fundamental photo-physical research and industrial applications, with the advantages of lower hardware cost as well as higher imaging speed.