One-side optical horizontal deviation is one of most important parameters to evaluate the quality of assembled spectacle products. This article introduces a novel measuring method of laser line positioning, which can measure the one-side optical central horizontal distance and deviation quickly and accurately. Its measurement uncertainty is calculated. Meanwhile it is compared with other related methods for analysis, laser line positioning is an effective way to evaluate the quality of assembled spectacle products for its simplification in equipment used, convenience in operation and accuracy in measurement.