The traditional testability demonstration sampling methods do not consider the working condition factor, resulting in sample sets that fail to reflect the true testability level of the system. To address this issue, a sampling method combining the coverage adequacy and risk methods based on the division of working conditions is proposed. The method utilizes the consideration of the integrated failure rate of multiple working conditions as well as the adequacy additions for each working condition separately, and the resulting sample set can achieve the coverage of working conditions, structure, and function, which improves the accuracy of the testability test results. This method utilizes the comprehensive failure rate considering multiple working conditions factors and the adequacy additions for each working condition separately. The resulting sample set can achieve the coverage of working conditions, structure, and functions, thereby improving the accuracy of testability demonstration results. Finally, a case shows the validity and feasibility of the method.