Real-time polymerase chain reaction（PCR） is a method for rapid replication and quantitative detection of specific DNA fragment through thermal cycle and fluorescent signal detection.The precision of temperature control in thermal cycle determines PCR efficiency

and also affects the precision of quantitative detection.According to the theory of unsteady state heat transfer

heat takes time to transfer from block to test solution.In order to know the influence of the delay time on temperature control

a data acquisition has been designed using USB bus and FPGA technology based on NTC thermistor

and continuous data acquisition is achieved through multi-threading technology and buffering queues.By the combination of theory and experiment

the delay time of heat transfer has been measured successfully.