Abstract: The traditional Chinese theatre was often built with a courtyard. In such kind of space, the absence of a roof would mean little reverberation and non-diffused sound field. Acoustically the situation is quite different from that of any enclosed space. Therefore, the classic room acoustics, such as Sabine reverberation formula, would no longer be applicable here due to the lack of sound reflections from the ceiling. As the parameter of reverberation time T30 shows the decay rate only, it would not properly characterize the prominent change in the fine structure of the echogram, particularly for the case with a large reduction of reflections during the decay process. The sense of reverbrance in a courtyard space would differ noticeably from that of the equivalent 3D-T30 in an enclosed space. In this article, the author, based upon the characteristic analysis of the sound field in a courtyard space, presents a preliminary study on the acoustics of the courtyard theatres.