This study proposes an optical method to improve the yield efficiency of QPCR. The concept is that the conversion efficiency of fluorescent dyes is not high, and the light intensity signal is weak and difficult to distinguish. Therefore, the intensity signal of the excitation light source is reduced to obtain the fluorescent signal. Using the DNA binding dye as a model, the excitation light signals captured by the different angles between the incident light and the speculary reflected light are used to determine the correct fluorescent detection position, and to explore the efficiency of the test tube diameter for capturing fluorescent signals. The simulation results show that the standard diameter test tube has a minimum noise interference at the 45 degree position, which means that the fluorescent signal can be intercepted most effectively. This method does not change any chemical configuration and process conditions, saves a lot of time and process steps, and has high stability and zero pollution.