The urgency of the problem lies in the fact that the development of methods and mathematical models of the measurement s-parameters in the coaxial paths in the scientific and practical aspects enhances the accuracy and adequacy of measuring S-parameters of active microwave circuits, for the improvement of the work of the microwave technology, to ultrahigh frequency range, which in turn, increases the cost-effectiveness of production. The task of ensuring the continuity of the parameters of standard measures within its operating frequency range these days is one of the important tasks in the field of metrological assurance of measurement of parameters of complex reflection and transmission phase and module in coaxial paths. This problem is due to the fact that the certification standard measures have a finite set of experimentally determined parameters of these measures and the consumer need to know the parameters of the measures at any point of the frequency range. spline- interpolation was used to solve this problem. A serious drawback of the previously used methods of measurement of radio circuits maintain the unity of their parameters is some isolation from the existing measurement methods and measurement error analysis methods that are not allowed to use the opportunities of high-precision measurement methods and algorithms to improve the accuracy of devices supporting traceability and vice versa. The purpose of this article - the creation of new methods and mathematical models of highprecision measurement of S-parameters, ensuring their use in any point of the frequency range with high accuracy through the use of spline functions.