A major effort in ultrashort and ultrafast optics is to obtain subfemtosecond pulses from high harmonics generated by interaction of an intense short-pulse laser and a jet of rare gases. The chirped multilayer mirror in the extreme ultraviolet region can be used to select some high harmonics and compensate the chirp. It is an effective element for the production of subfemtosecond pulses. The mechanism of obtaining subfemtosecond pulses from high harmonics by using the mirror was presented. The chirp of high harmonics in specified experiment condition was calculated. The chirped multilayer mirror was designed by using a genetic algorithm. Its capability of producing subfemtosecond pulses was shown by numerical simulation. Results indicate that the designed chirped multilayer mirror can be used for production of 132 as pulses.