A new image measurement and calculating method was proposed to improve the measurement accuracy and adaptability of auto lensmeter. Firstly, 16 dots infrared image driven by constant pulse current was received with CCD. Secondly，image was processed by high speed CPU system, and binary image was divided up by CPU system. Finally, we can acquire the diopter parameter of glass by least square method. The experiment was carried out using the standard glass and the glass with nick and dirt. Compared with 4 dots method, results show that the measurement errors are less than ±0.06 D which was minimum error of diopter prescribed by National Metrology Bureau. In addition，the accuracy of the glass with nick and dirt was improved obviously, and adaptability of environment was also enhanced.