Linear thermal expansion of PuO2.00 was evaluated by an experiment and a molecular dynamics (MD) simulation. In the experiment, thermal expansion of a sintered PuO2.00 pellet of 95.0%T.D. was measured with a dilatometer in the temperature range from 300 K to 1923 K. In the MD simulation, lattice constants of PuO2 were evaluated in the temperature range from 300 K to 2800 K, and then the thermal expansion was evaluated. The experimental thermal expansion data were in good agreement with the MD simulation results. A suitable equation for thermal expansion of PuO 2 in the temperature range from 300 K to 2800 K was derived from both data sets.