To provide a method for synthesizing in a large amount an accelerated phosphorescent substance excellent in brightness, erasability and residual image characteristics, and to provide the accelerated phosphorescent substance thereby.

The method for the preparation of an accelerated phosphorescent substance, comprises the following burning processes; (a) filling a phosphor precursor in an amount of 4-1000 kg in a burning reactor inside, (b) passing at a flow rate relative to the volume of a reactor core tube of 0.01-1.2% through an atmosphere containing less than 0.1% of oxygen and 0.1-10% of hydrogen with heating up to 600°C or higher, (c) passing at a flow rate relative to the volume of the reactor core tube through an atmosphere containing 0.1-7% of oxygen and 0.1-10% of hydrogen with heating at 600°C or higher and 30 min. or longer, (d) passing through the same atmosphere as (b) at a flow rate relative to the volume of a reactor core tube of 2.0-10% with heating at 600°C or higher for 30 min. or longer, and (e) passing through the same atmosphere and flow rate as described in (d) with cooling the substance down to 100°C or lower.