This article studies the changes of the Pmax、Vcrcurves corresponding to OLTC adjustment within the static scope by using the ternary analytical method, and states the influence of OLTC transformer ratio change on static voltage stability limit of power system connected DG,and it carries on the simulated analysis of the 2machine system in this paper. Such conclusions have been drawn as followings: OLTC transformer ratio adjustment changes the maximum transmission power and critical voltage of the power system,and effects the Stable operating range of power system, OLTC transformer ratio change effects the degree of influence on the Pmaxand Vcr differently due to distribution systems connected DG.