In order to check the reliability and accuracy of bill hooks biting ropes in the knotting process of Deerting knotter, the space trajectory equation of key positions related to knotter and biting was solved with the help of mathematical analytical method. The general evaluation equation to predict the existing knotter structure, matching relationships between motions was established according to the position and movement requirement of knotter hooks rope-biting. In addition, a visual demonstration of the matching relations between the existing knitter structure and motion parameters was produced by means of Matlab. Such methods had a predictable effect on different designs of knotter hook and twine retainer, and directive function in revising data and adjusting information.