Hydrate layers are common in deep water environment with low temperature and high pressure. During surface casing cementing, hydration and heat release of cement slurry in deep water is easy to decompose natural gas hydrate and lead to formation instability, which brings great risks to deep water cementing. Based on the decomposition characteristics of natural gas hydrate at low temperature, high pressure and electrolyte, a low-hydration hot cement slurry system was successfully developed, with Portland oil well cement as the base material and the addition of self-developed micro-capsule type thermal control material (PCM-1). In the early hydration process of the cement slurry system, the temperature was continuously measured by self-developed semi-adiabatic test equipment, and the hydration heat control effect was characterized by the maximum temperature (Tm) and the maximum hydration temperature rise (Tr) of the cement slurry system. The results showed that compared with pure slurry cement system, hydration maximum temperature decreases by 21.1℃, when 15 wt% PCM-1 was added. At the same time, the maximum hydration temperature rise decreased by 23.6℃. In addition, 24 h and 48 h hydration heat respectively decreased by 7.68?104 J and 7.28?104 J. This technique can effectively control the hydration temperature rise and hydration heat of cement slurry, greatly reducing the cementing risk of hydrate layers in deep water.