A low resolution global circulation spectrum model, using primitive equations, which can be appliedto climate simulations and sensitivity tests is described in this paper. The model has three levels in its vertical direction and a spherical harmonics representation with a ten-wave rhomboidal truncation in its horizontal direction.Some physical processes, such as radiation,convectiye adjustment, large-scale condensation and surface fluxes are also included. Global distribution of climates for January and July are simulated by using the actual zonal average field as the initial field. The simulated monsoon rain belt is especially close to the observation in the model. Therefore,the model is useful in the investigation of the climatic changes and the formation and maintenence mechanism of monsoon in China.