Micro-Electro-Mechanical System(MEMS) packaging stress is a residual stress produced by MEMS packaging process, which has significant influence on the thermal stability and long-term stability of MEMS devices. An accurate assessment of stress is useful for the studying of packaging stress. Because the package stress is too low to be directly measured by the existing techniques, a novel measurement method based on stress magnifying structure and micro-Raman spectroscopy is proposed to obtain the average package residual stress in MEMS devices. Based on the theoretical analysis, the magnification ratio between the original package model and the stress magnifying structure is obtained, and a design rule of the stress magnifying structure is given. Then, a Finite Element Modeling(FEM) of a kind of high precise MEMS micro-accelerometer is conducted to prove the theoretical analysis result. Finally, for the package residual stress measurement of the micro-accelerometer, fabrication and package are successfully performed. Then stress measurement experiment is conducted to measure the magnified package stress and to calculate the actual average package residual stress in the micro-accelerometer, showing an identical result with previous simulation, which proves the measurement method much reliable.