To address the issue that existing testability metrics assessment methods do not consider the impact of various operating conditions over the equipment"s lifecycle, leading to results that fail to reflect the true testability level of products, this paper proposes a testability metrics assessment method that accounts for multiple operating conditions. First, the meaning of operating conditions is investigated, followed by an analysis of their influence on testability metrics. A sample logic synthesis method for testability metrics under multiple operating conditions and a Bayesian-based assessment method for these metrics are introduced. Case analysis results demonstrate that the proposed methods are simple and efficient, effectively resolving the shortcomings of traditional assessment methods in evaluating testability metrics under different operating conditions.