Probabilistic relational databases play an important role on uncertain data management. Informally, a probabilistic database is a probability distribution over a set of deterministic databases (namely, possible worlds). The existing initialization methods that transform the possible worlds representation into our chosen representation, make the formulae of tuples very long. An efficient initialization method is proposed by providing an equation that can generate simplified formulae of tuples. The experimental study shows that the proposed method greatly simplifies the formulae of tuples without additional time cost. The subsequent queries benefit from the simplified formulae of tuples.