Based upon the experimental study on bed-making of wandering braided river channel by using process-response model method, both the spatial and temporal channel evolution processes are analyzed. It is found out that the spatial and temporal processes can substitute each other by comparing the horizontal processes and the variations of variables of river channel system. Thus, the existence of ergodic hypothesis in laboratory which provides a new evidence for the hypothesis. Based upon this finding, the complex response can be subdivided into spatial complex response and temporal complex response according to the objective situation, and the concept of temporospatial complex response is consequently put forward and verified with the experimental data. In fact, S.A.Schumm and Jiongxin Xu have only studied the temporal complex response, but rarely mentioned the spatial complex response. Experimental study illustrates that there is a temporal complex response in the same region at different stages and a spatial complex response at the same time in different regions under certain conditions. Temporal complex response is often and firmly related to spatial ones and can be substituted for another one according to the ergodic hypothesis, and vice versa. It is so called temporospatial complex response.