Abstract: After the knitting process was observed on the flat machine, forecast model of the stitch length for rib fabric was established basing on certain assumptions through analysis and deduction. Feasibility of the model was verified by the comparison between the measured and predicted stitch length of the rib fabric under the setting conditions. The results revealed that the stitch length of rib fabrics showed a good linear relationship, respectively, with pressure needle depth and needle bed gap. According to the model, scale on the flat machine head can be reset, which is convenient in production control and can quickly determine the stitch length, provides a basis for yarn budget and cost accounting.