Monitoring tire pressure conditions and issuing timely warnings of tire deflation are important to ensure driving safety and avoid unnecessary fuel consumption. Although installing pressure sensors is a direct and accurate monitoring method, it may raise system cost and complexity. The indirect monitoring method with no reliance on pressure sensors is attractive for economical cars. This paper proposes a fusion-based indirect tire pressure monitoring method using existing on-board wheel speed sensors. The screening basis of reasonable wheel speed signals was determined by data mining of typical driving scenarios. Three typical signal distortions were effectively corrected to ensure the signal quality. Tire deflation analysis methods based on time and frequency domain signals were designed and fused using fuzzy logic. Validation results of the proposed two analysis methods and their fusion strategy showed that the proposed fusion strategy can achieve more comprehensive tire deflation monitoring with fast response and high accuracy.