Experiment methods using water as medium was adopled to study the flow and heat transfer in coaxial spiral tube to tube heat exchanger with Reynolds range from 30 000 to 100 000,and experiment research was carried out on two tubes with different helical pitch for their frictional resistance and heat transfer performance.The study shows that the tube frictional resistance coefficient of coaxial spiral tube to tube heat exchanger is 3 to 3.5 times as large as circular tube exchanger.The flow field characteristics outside and inside the coaxial spiral tube to tube heat exchanger tubes are revealed using numerical methods.