Gross primary production (GPP) is the total amount of atmospheric carbon (CO2) assimilated by vegetation. In this article, a regional terrestrial ecosystem GPP estimation model REG-PEM(REGion Production Efficiency Model) is developed based on light use efficiency theory, and 8-day composite and annual GPP are calculated using REG-PEM model in Jiangxi province. The REG-PEM model was designed on the basis of the production efficiency concept in which gross primary production is calculated from the products of the photosynthetically active radiation (PAR) absorbed by the vegetation(APAR) and light use efficiency, and all the input data get from remote sensing method. GPP are calculated using MODIS 8-day composite products and total ozone mapping spectrometer (TOMS) reflectance data in Jiangxi province in 2003 and 2004. GPP increases in spring, reaches maximum in summer and decreases in autumn, and fluctuates in the year. The results indicate that the REG-PEM model is capable of tracking seasonal dynamics and interannual variations in GPP at a 8-day temporal resolution.