According to the principle of GEM model,writing the optimization problem and solving it,it is proved that GEM model has the same expression as those of Gravity model and Detroit model.

• 根据重力式熵模型的原理写出其规划问题；求解并进行等式转换；证明了重力式熵模型与重力模型及底特律模型具有相同的表达形式；并在实际规划问题中应用三种模型进行预测.