In heat exchanger heat meter, the heat exchanger is equivalent to a flowmeter. The flow and heat can be calculated by measuring the inlet and outlet temperature of heat exchanger. It greatly prevents the flowmeter from the problem of inaccuracy and damage which are caused by the quality of water. However, due to the complexity of the heat exchanger model, it is difficult to get an expression between flow and temperature through analytic methods. This makes a great difficulty to design and optimize the structure of heat exchanger. To solve the problem above, we establish a three-dimensional model of heat exchanger by means of CFD numerical simulation software. By solving it in the parallel computing platform, we get the relationship between flow and temperature difference ratio, and optimize the structure of the heat exchanger by means of pattern search method. Simulation results show that after using this optimization method, the performance of heat exchanger has been effectively improved.