Abstract: Wire arc additive manufacturing (WAAM) is an effective method for preparing magnesium alloy components with excellent performance and complex configurations. However, this technology is prone to severe thermal accumulation during the preparation process, which further leads to defects such as coarse alloy microstructure and poor forming performance, limiting its application and promotion. To solve this key problem, AZ31 magnesium alloy was used as the experimental material in this paper, and a series of AZ31 magnesium alloy thin-walled samples with different interlayer pause times were prepared by adopting the interlayer pause strategy, and their microstructure and mechanical properties were systematically studied. The research results show that after inter-layer pause treatment, the microstructure of AZ31 magnesium alloy is significantly optimized: the grain size is remarkably refined, the grain orientation distribution tends to be more random, and the second-phase particles are also finer and more uniformly distributed. The improvement of microstructure effectively realizes the synergistic improvement of alloy strength and plasticity. Among them, when the interlayer pause time is 60s, the alloy sample exhibits the best comprehensive mechanical properties, with the yield strength, tensile strength and elongation reaching 116MPa, 250MPa and 18.1%, respectively. It is concluded that the interlayer pause strategy is an effective means to alleviate the severe thermal accumulation in the arc additive manufacturing process, which can realize the in-situ regulation of the alloy microstructure. Its research ideas and technical methods can also provide important reference and application for the arc additive manufacturing of other alloys.