1. A system for reusing triple event data of positron emission tomography, a plurality of data is generated by an object undergoing the positron emission tomography scan, the system comprising: an input unit, used to receive the data; a determining unit, connected with the input unit, determining the data received from the input unit, picking out data corresponding to triple event from the data, according to a formula to pick out data corresponding to coincident event from the data corresponding to triple event, reusing and analyzing the data corresponding to coincident event to generate an analysis result; and an output unit, connected with the determining unit to output the analysis result.