The group delay characteristic is the important test item of transponder payload in telecommunication satellite, and the digital method of group delay test is mainly used for the level of 10MHz bandwidth transponder test. With the development of satellite payload technology, the bandwidth of communication is also diversified rang from narrowband transmission of military satellites (level of 10kHz bandwidth) to high-throughput satellite (level of 100MHz bandwidth). The difference of the transponder bandwidth puts forward higher requirements for group delay test system design. Through theoretical analysis, MATLAB simulation and hardware test and verification, the paper is mainly to optimize the algorithm and parameter of test technology to meet the different transponder bandwidth test requirements.