A 16-blades-disk of flat plate is made as a test and mathematical model to study the effects of blade mistuning on the dynamic characteristics of bladed-disk assembly, as well as the effects of mistuning amplitude,mistiming order and six distribution types of mistuning on the response to forced vibration. The results show that the natural mode of a tuning system can be categorized into single-mode and double-mode. Mistuning separates the double-mode into two modes of similar frequency. The response to forced vibration of a mistuned system is greater than that of the tuning system and the former will rise with increase of mistuning amplitude. At the same exciting frequency the influences of the various distribution types on the response to the forced vibration are different, that is to say, there exists an optimal distribution type. The blade bearing the greatest response is generally the extremely mistuned one, and there certainly exists one or more blades bearing the greatest response at any exciting frequency. This might be one of the causes leading to damage of one or more blade.