In order to solve the prolem of cophasing detection for the segmented mirror of telescope, the piston errors measurement of segmented mirror by the broadband and narrowband ShackHartmann algorithm are theoretical analyzed and simulated, and an active optics and cophasing experiment system is built. The segmented mirror is consisted of four hexagonal segments with the flat to flat lengths of 100 mm and the curvature of radius is 2 000 mm. Firstly, the ShackHartmann is used to detect the errors of cofocus ,and the active optics is used to control piezoelectric actuators to realize the fine cofocus of segmented mirror. Then the broadband phasing algorithm is used to realize the measurement of corse cophasing of segmented mirror. Finally, the narrowband phasing algorithm is used to realize the measurement of fine cophasing of segmented mirror, and the active optics is used to control piezoelectric actuators to realize of the segmented mirror cophasing adjustment. The experimental results show that the range is dozens of micros and the measurement accuracy is better than 15 nm of broadband and narrowband phasing algorithm, which demonstrates that the methods are suitable for the segmented mirror cophasing measurement and adjustment.