In this study, a thermoelectric energy harvesting device based on phase change material is presented which can be applied with large temperature variation in space for power supply. Aiming at multi-parameter optimization of thermoelectric harvester, an assessment of the generalized design rules for the proposed harvester has been implemented. The effect of thermal conductivity, melting temperature and mass of phase change material on the thermodynamic process were investigated to obtain the design criterion for thermoelectric harvester. Besides, both simulation and experiment validated that choosing PCM with a suitable melting temperature is quite essential to the temperature control by balancing the heat storage and release process, consequently enhancing the power output. This work offers a unique powering solution for wireless sensor involving location with temperature variation in space application.