Multilateral wells technology is a new technology after the horizontal well. The application of this technology has significant technical and economic advantages because of space limitations of offshore platform for oilfield development. But with continuously increase of multilateral well quantity, it was very important to forecast its productivity precisely to reduce development risk of the oilfield.Basing on green’s function and source function, the potential distribution of arbitrary trajectory well in box shaped closed reservoir was derived using superposition principle and mirror reflection method. The pressure drop model of variable mass flow in wellbore was derived according to conservation of mass and momentum. And, finally the two models above are coupled according to continuity equation to form the productivity prediction model for arbitrary trajectory well. The effects of lateral location, different angles and lateral symmetry on the production of multilateral wells are analyzed using this model. The numerical results indicate that the increasing the angle between laterals and the main wellbore can reduce the interference among them. When the angle is restricted by drilling technology, prolonging the length of each lateral can increase the productivity of the multilateral well. Laterals should be disposed in the heel section of the main wellbore with an asymmetric distribution, which is beneficial to enhancing the productivity of the multilateral well.