An adaptive algorithm for controlling the chaotic optical system, termed as the neural network adaptive control algorithm in which the system identifier of the controlled chaotic optical system is a BP NN, is presented in this paper. In this NN adaptive algorithm the difference between the output of the controlled chaotic optical system and that of the trained NN identifier is employed as the negative feedback in readjusting the system's control parameter. Because the NN identifier can reconstruct the dynamics of the controlled chaotic optical system from the output time series with the support of the BP algorithm, this adaptive control algorithm is considered applied to control the chaotic optical system when the reference model for control can not be obtained in advance. The feasibility of this NN adaptive control algorithm is demonstrated with the computer simulation of identifying and then controlling a Bragg diffraction acoustooptic bistable system.