Transactional memory is a new multiprocessor architecture intended to make parallel programming easy and efficient. Signaturebased conflict detection is a promising approach in transactional memory systems and its rate of false positive has much influence on its performance. The GHB algorithm is an excellent algorithm with a lower false positive rate, but high hardware cost. In this paper, we propose an improved PGHB algorithm based on GHB. The experimental results show that our improvement gains a compromise between the hardware cost and the false positive rate.