Abstarct: Prediction the behavior of the roof in caving and face advance is the main factor in economics of the longwall method.the success factor in longwall mining is roof control and prediction of roof behavior in caving zoon. Determine the length of First roof weighting effect and periodic roof weighting effect on the roof of caving zone will help. Sudden and unexpected roof fall not only does it endanger the safety of employees but also destroys and damages the extraction equipment and components, and by interrupting the extraction operation creates a problem for economics of Mining. Exist several methods such as experimental method, analytical method, physical modeling and numerical modeling to determine the length of First roof weighting effect and periodic roof weighting effect. baxsed on the results obtained by researchers and their agrement for numerical modeling, this method is selected for this thesis. Determine the length of first roof weighting effect and periodic roof weighting effect in E3 panel in the tabas parvadeh coal mine in this thesis.confirmation of failure in the roof baxsed on Sakura criteria and validation of the model was made by comparing the instrumentation data and the amount of displacement obtained from the numerical modelling. baxsed on the work carried out in this research, the length of the length of first roof weighting effect is 11 meters and the length of the periodic roof weighting effect is 2.5 to 4.5 meters. baxsed on the modeling done by increasing the modulus of elasticity, the displacement of the roof has decreased and the decrease of the modulus of elasticity has been accompanied by an increase in the displacement of the roof. baxsed on this analysis, it can be said that increasing the modulus of elasticity increases the length of the first roof weighting effect and reducing it will reduce the length of the the periodic roof weighting effect and hanging wall.