The packaging induced stress is the main factor impacting the threshold current, the characteristics of laser, and the life time of laser diode arrays (LDA). A method is imperative to measure the packaging induced stress in the LDA. The basic theory of stress affecting the electro-fluorescence degree of polarization (DOP) of LDA is stated. Electro-fluorescence DOP of high power LDA is measured. Results show that the DOP of LDA change obviously when the driving current grows. LD arrays in different packaging ways are tested. The DOP of the LDA under test is sensitive to stress. When pressure is applied to the center of the array, the distribution of DOP along the array undulates acutely. According to the DOP test of a lot of components, some characteristics within big package-induced-stress are obtained. The result shows that the distribution of stress induced by different materials and different packaging ways is distinctive from each other.