The invention relates to a detection method of hydration resistance of a MgO-CaO material. The detection method comprises following steps: the MgO-CaO material to be detected is smashed until particle size d ranges from 2.80 to 3.00mm so as to obtain a MgO-CaO material sample to be detected; water with pH value of a0 is delivered into a first beaker, the MgO-CaO material sample to be detected is added at a liquid-solid mass ratio of 1000:1, an obtained mixture is allowed to stand for 20min at 25 DEG C, and then is filtered; a hydration solution obtained via filtering is delivered into a second beaker, and is allowed to stand for 20 to 30min at 25 DEG C, the pH value of the hydration solution in the second beaker is detected to be a1, and then the hydration resistance index of the MgO-CaO material is calculated based on a formula disclosed in the invention, and the hydration resistance index eta of the MgO-CaO material can be detected for n times via the above steps, and the average value eta is obtained. The detection method is simple; period is short; precision is high; suitable range is wide; and safety performance is excellent.