Clamping force is a crucial parameter in injection molding. Improper clamping force setting can result in poor product quality and shorter machine lifespan. The objective of this study was to establish an eigenvalue-injection clamping force peak value by real-time clamping force measurement with strain gage sensor for prediction, adjustment, and control of injection product quality. In this study, computer-aided engineering (CAE) structural analysis technique was used to analyze and verify the points of measurement of the sensor. Next, the molded product was conducted using the following injection molding parameters: V/P switchover point, clamping force, injection speed, melt temperature, mold temperature, packing pressure, and packing time. The relationship between injection clamping force peak value and product quality were examined. The results showed that CAE analysis could successfully predict and provide suitable points for sensor measurement. Comparison of analysis and experiment results revealed that injection clamping force peak value and part weight exhibited identical trends. Finally, the injection clamping force peak value not only could it successfully predict product quality, but also it would achieve the purpose of optimizing and stabilizing the clamping force and part weight.