The invention discloses a calcination process of active lime. The calcination process adopts a preheating-suspension calcination device comprising a multi-stage cyclone preheating system, a decomposing furnace and a multi-stage cyclone cooler. The calcination process is characterized in that limestone powder which is broken and homogenized into blocks is ground into fine powder, the fine powder is placed in a storage tank for homogenization, then preheated by the multi-stage cyclone preheating system and sent to the decomposing furnace for calcination, thereby preparing the active lime, and the active lime is further cooled by the multi-stage cyclone cooler for obtaining the active lime; wherein the main control temperature of the decomposing furnace is 850-950 DEG C; and the calcination time is 3-5 seconds. The calcination process utilizes the preheating-suspension calcination reaction method for calcining the active lime, and fuel can use low-grade fuel-biluminous coal. Compared with the traditional process, the calcination time is short, the effective utilization rate of the lime product is high, the product quality is stable, the energy consumption is low, and a production region has no environmental pollution; meanwhile, the calcined active lime is the fine powder, the use is very convenient, and the range of applications is broader in comparison with the active lime calcined by the traditional process, thereby being conductive to promotion and implementation.