Photosynthate allocation is critical to crop growth and biomass formation, and it is also a key part of crop simulation. A photosynthate allocation model of maize was established based on photosynthate allocation mechanisms as well as the photosynthate allocation characteristics of maize at different stages. This model was then coupled with the CO2 assimilation module of WOFOST crop model to simulate the biomass dynamics of different organs of maize on daily scale. It was validated by 5 years' field experiment data of spring maize from Jinzhou Agricultural Ecosystem Research Station. The results showed that, the model could explain about 95.4% of maize's total biomass change, while 87.0%, 85.3%, 67.9%, 76.5% and 87.5% of vegetative, leaf, root, stem, and ear biomass variations, respectively. This model could fulfill accurate simulation of different organ biomass dynamics of maize.