Based on classical methods of the non-linearity property of the non-linearity regression model, analysis of its limitation is made. This paper promotes a new method about local approximation through the discussion for the convergence of some models, which remedy the defect of the traditional ways. The asymptotic property of least square estimator and the method of iterative initial value selection are studied. And a new trend for the method to measure the model´s non-linearity is given.% 利用传统曲率理论度量回归模型的非线性程度，分析其缺陷，并对几类实例模型进行探讨，进而提出基于局部近似的新度量方法，在一定程度上弥补了传统方法的缺陷；还研究了模型参数基于局部线性近似的最小二乘估计的渐进性质及其求法中迭代初值的选取和改进方向。
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