P-type oxide semiconductor gas sensors have gained increasing attention for their distinctive catalytic activity, high oxygen adsorption, and high humidity resistance. However, the low gas response of p-type sensors restricts their utilization, prompting numerous attempts to overcome this limitation. In this study, we have successfully engineered a promising p-type gas sensor by increasing the dielectric constant and optimizing crystal symmetry, departing from conventional approaches such as reducing particle size, constructing complex heterojunctions, and decorating with noble metals. The as-prepared multiferroic Bi0.92Dy0.8FeO3 gas sensor exhibits a well-defined gas response to acetone, demonstrating ultralow detection limits, distinctive selectivity, high humidity resistance, and long-term stability. Through comparisons of crystal symmetry, morphology, specific surface area, atomic chemical environment, dielectric properties, and sensing properties among a series of Dy3+ doped BiFeO3 solid solutions, we attribute this extraordinary sensing performance of Bi0.92Dy0.8FeO3 to its higher dielectric constant and unique domain-wall structure arising from its non-centrosymmetric crystal structure. This work provides additional perspective for preparing high-performance gas sensors.