Abstract: In this paper,we utilize the variational method in the initialization for a barotropic primitive equation model.As a dynamic constraints,the differences between the observed and analyzed fields are at it's minimum subject to the quasigeostrophic relations or the requirement of quasi-steadiness for the primitive equations,and it is required to make the loss of total mean kinetic energy over the analysis area to be minimum.24-hours 500 mb height forecasts are made and compared with those obtained in taking the geostrophic winds as initial fields.In next experiment some observed data are partly used in the initial field.The forecasting results are improved.The influence of the variational constraint on perturbations are also discussed.