A method for calculating a total transmission probability within a social network based on timing includes a path probability calculating step, a first binary-addition tree searching step, a second binary-addition tree searching step and a transmission probability calculating step. The path probability calculating step is performed to calculate a plurality of time-path probability matrices from the social network. The first binary-addition tree searching step is performed to enumerate a plurality of feasible spread vectors and a plurality of 1-lag temporal vectors. The second binary-addition tree searching step is performed to enumerate a plurality of time-slot vectors of each of the 1-lag temporal vectors. The transmission probability calculating step is performed to calculate the total transmission probability of the social network. The time-path probability matrices are corresponding to a plurality of time values, and the time values are in the specific time and different from each other.