In textile, the application of analytical mechanics can be found in a spinning process. The aim of this research is to determine a model as well as to predict the yarn strength of ring- spun yarn influenced by the yarn count number (in unit m/g) and also the delivery speed of yarn (vf). In this article, the yarn count and the speed of delivery roll of ring-spun yarn were studied comprehensively, and based on this, a ring-spun yarn strength prediction model has been found and established by analytical mechanics.