Based on single vendor and single buyer, vendor supplies buyer with a product, and the vendor split order into many equal shipments to delivery. Aimed at minimizing the total cost of vendor and buyer, JIT purchase model based on actual freight rate was proposed. Actual freight rate is transformed into alternating ranges of a constant charge per kilogram followed by a constant fixed charge. For the actual freight rate, by calculating the solutions for all weight ranges and comparing them, the optimal solution was derived. Numerical results show that the algorithm can obtain the optimal solution, and the model is verified.