Abstract: The Dalazi formation, located in Jilin Province, is regarded as a typical horizon of the early Cretaceous in Northeast China. However, its age has been much debated, so the study attempts to explore its age based on the detrital grain fission track thermochronology. It is concluded that zircon and apatite fission track ages from the Dalazi formation are 100 Ma and 95 Ma or so, respectively. Integrated with the regionally geological features, they are probably interpreted as the cooling ages derived from the uplift and exhumation of their source rocks. Thus, the geological age of the Dalazi formation is no more than 100 Ma, and most likely of late stage of the early Cretaceous．