Usually mathematicians use Hodgkin-Huxley model or FitzHug-Nagumo model to simulate action potentials of skeletal muscle fibers. These models are electrically excitable, but skeletal muscle fibers are stimulated chemically. To investigate skeletal muscle fibers we use a model with six ordinary differential equations. This dynamical system is sensitive to initial value of some variables so it is more realistic. Studying qualitative behavior and propagation of action potential through a cell with this model is time consuming .In this paper we try to use properties of variables of this model to reduced dimension of this dynamical model. We study qualitative behavior of obtained model and illustrate that this new model treats like the original model.