Abstract: Debt has long been regarded as "the god" in China's rapid economic growth in the past and was dismissed as "the devil" as economy step into a "new normal" phase at current. In fact, the debt itself has not "good and evil" points, and universal optimal debt arrangements shouldn’t exist, so a reasonable debt arrangement should adapt to the size and stage of development economies. To explore the optimal conditions of debt for economic growth target, this paper found that there is a mutual restraint between China's debt and there exists a "optimal solution" during the “double growth" of debt scale and debt structure by doing empirical research based on the Provincial Panel Data. Before the optimal solution, either the growth of debt scale or public debt ratio will bring economic growth, but after reaching this limit, to achieve economic growth , only by making trade-offs between reducing debt scale or restructuring debt. The optimal solution of the regional debt scale and debt structure is in the premise of the financial structure, financial revenue and expenditure, the proportion of state-owned investment and the urbanization rate. Then the robustness test verified the conclusions of this paper again. At last, some relevant policy recommendations have been put forward based on the conclusions of this paper.