There is no engineering experience to learn from the use of gabbro aggregate roller compacted concrete gravity dams, which is a new material and technology, so it is necessary to combine the engineering raw materials to carry out the research on the thermal diffusivity of roller compacted concrete. In this paper, the field sampling method is used to test the thermal diffusivity of two design indexes of crushed concrete in TB Hydropower Project, and the results show that: the thermal diffusivity of the roller compacted concrete with design indexes of C₉₀20W8F100 and C₉₀15W6F100 are 3.81×10^-3, 3.82×10^-3m²/h, respectively, and the values are close to each other; it was found that the thermal diffusivity of the roller compacted concrete decreased with the increase of the age of curing in the test