The obscuring ratio is an important parameter to assess the smoke obscuring performance, two methods for testing the obscuring ratio of infrared smoke are proposed, which are the temperature contrast method based on single blackbody and the electrical level difference method based on double blackbody. The testing principles of the two methods are analyzed and experimental verification is performed. According to analysis and comparison, the test error is less than 3.5% and the scenarios suitable for the two methods are presented.