Objective: Sacituzumab govitecan (SG) is a novel antibody-drug conjugate (ADC) that targets Trop-2, a cell surface antigen commonly overexpressed in various epithelial cancers, including mTNBC. It has been proved that the efficacy of SG is highly dependent on Trop-2 expression, with higher expression levels potentially correlating with better treatment outcomes. The cost-effectiveness of SG relative to standard chemotherapy regimens in the treatment of TNBC in the context of varying Trop-2 expression levels is eagerly needed. Methods: The Weibull approximation was applied to further calculate life expectancy of the SG and chemotherapy based on phase III ASCENT study. The partitioned survival model (PSM) was then developed, followed by one-way sensitivity analysis and probabilistic sensitivity analysis to assess the stability of the parameter values and assumptions used in the model. Results: For patients with high Trop-2 expression, SG treatment gained 0.75 QALYs at a cost of $123406, while single-agent chemotherapy treatment gained 0.41 QALYs at $1557. Despite more QALYs, SG was significantly more expensive, resulting in an ICER of $357133/QALY, far above the cost-effectiveness threshold in mainland China ($12734-$38202). Thus, SG is not cost-effective compared to chemotherapy for high Trop-2 expression mTNBC. Similarly, for medium Trop-2 expression patients, the ICER for SG vs. single-agent chemotherapy treatment was $281567/QALY, also exceeding the threshold. For low Trop-2 expression patients, SG gained more LYs but fewer QALYs than single-agent chemotherapy treatment, making it not cost-effective compared to chemotherapy. Conclusion: In conclusion, while sacituzumab govitecan is clinically effective for mTNBC, its high cost makes it economically unfeasible in mainland China. A substantial price reduction is essential for it to become a viable option, enabling more patients to benefit from its therapeutic potential.