The surface temperature of extruded AZ31B alloy plate was measured by infrared thermograph in air during tension and high-cycle fatigue tests. The mechanism of heat production was discussed and the value of critical fatigue damage temperature was calculated according to the P-∆T curve. Results show that the variation trend of temperature is different between tension and fatigue tests. The temperature evolution in tension test consists of four stages:linear decrease, reverse linear increase, abrupt increase, and final drop. The initial decrease of temperature is caused by thermal elastic effect, which is corresponding to the elastic deformation in tension progress. When cyclic loading is above the fatigue limit, the temperature evolution mainly undergoes five stages: initial increase, steep reduction, steady state, abrupt increase, and final drop. The peak temperature in fatigue test is caused by strain hardening that can be used to evaluate the fatigue life of magnesium alloy. The critical temperature variation that causes the fatigue failure is 3.63 K. When ∆T≤3.63 K, the material is safe under cyclic loading. When ∆T>3.63 K, the fatigue life is determined by cycle index and peak temperature.% 采用红外热像仪测量挤压态 AZ31B 镁合金板材在拉伸和疲劳试验过程中试样表面的温度变化。对试样在不同载荷作用下的产热机制进行分析，并建立P-∆T曲线，对疲劳损伤过程的温度变化临界值进行计算。结果表明：AZ31B镁合金板材拉伸和疲劳过程中的温度变化趋势不同。拉伸过程温度变化包括4个阶段：线性降低、反向线性升高、温度陡升、最终下降。初始温度下降是由弹性拉伸阶段的热弹性效应造成。在循环载荷作用下，当载荷高于疲劳极限时，温度演化主要分为5个阶段：初始温度升高阶段、温度迅速下降阶段、温度稳定阶段、温度快速升高阶段、最终下降阶段。疲劳过程中的应变硬化造成初始温度升高至峰值温度，利用峰值温度与应力关系可以预测镁合金疲劳寿命。AZ31B镁合金达到疲劳极限时的临界温度变化为3.63 K。当∆T≤3.63 K时，材料在循环载荷下安全使用；当∆T>3.63 K 时，疲劳寿命取决于循环次数与加载初始峰值温度。
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