In order to check the conceptual design of subcritical reactor, an alternate depleted uranium/polyethylene-shell simulation device was established, to carry out uranium-238 neutron capture rate experiment using activation technique. The depleted uranium foils were activated at 90o to the incident. By measuring the 277.6 keV -ray emitted from 239Np generated by 238U (n, ) 239U reaction and correcting self-absorption of uranium experimentally, the 238U (n, ) reaction rate with an uncertainty between 3.5% and 3.7% and a total neutron capture of 2.24 0.09 of the system were obtained. The experiment was simulated using MCNP5 code with ENDF libraries. The simulations and measurements accord within 5% for the 238U (n, ) reaction rate and within 1% for the total neutron capture rate of 238U.