The cold shield structure has direct effects on stray lights suppressing in infrared detector. In order to further improve the cold shield efficiency, the cold shield height and containment structure influence on stray radiation suppressed were offered based on the analysis. Building mathematical models, DF20 cold shield was chosen as an instance to be calculated by the program. Compared with the test results of the infrared detector, when the cold shield height is 25 mm, the test result is 5.46%. When the cold shield height is 29 mm, the test result of cold shield which restraining the stray radiation effectively 4.87%, the test result of cold shield which restraining the stray radiation ineffectively 6.11%. A creative idea of cold shield structure design was proposed. Just increasing the cold shield height, may not increase the cold shield efficiency. When the baffles restrained the stray radiation effectively, with the cold shield hight increased, the stray radiation suppression capability became stronger, the cold shield efficiency increased, the infrared detector performance was improved. At the same time, changing the cold field structure will not influence the efficiency of the cold shield.