To reduce the smile effect caused by the thermal stress and to improve the beam quality of laser diode arrays, a set of optical system is designed for measuring the smile effect.By using an image amplification method, the smile effect of a laser diode array is accurately measured, and the measurement error is about ±0.1 μm.The quantitative characterization of the smile effect is a key technology to compare objectively the different measuring methods for smile effect and to reduce or eliminate the smile effect.According to analysis of the measurement results,the diode laser array package technique about reflow soldering is optimized, and the smile effect has been controlled within ±0.5 μm.As the smile effect values of the laser diode array is decreased and the beam quality of the laser diode array is improved significantly,the proposed method provides a technological fundation for development of small fiber diameters and high beam quality diode lasers.