Chahua Area( an area with no definite ownership between two areas) is a universal social phenomenon,and in different historical periods and different regions,the causation is different for each one.National administrative divisions are often the main reason for its formation,but if the cause is only explored from this aspect,while ignoring the deep restriction or limitation factors behind the national administrative decision,it will be difficult to reveal the root cause for its formation and tenacious continuation. In this article,the author makes a case study of Chahua Area in the lower reach of Qingshui River,trying to clarify and reveal the common features of its formation and continuation.