To improve the effectiveness of network learning platforms, this paper attempts to evaluate the usability of network learning platforms based on the perspective of users' experience and usability theory. With the support of the theory of usability, three dimensions to evaluate network learning platforms were given, and the relations between these three evaluation dimensions and usability were explained. Then, the three-level availability evaluation index system of network learning platform was established and discussed in detail. Finally, the theoretical model of the network learning platform usability evaluation system was proposed.