In Long Term Evolution-Advanced (LTE-A) network, Machine Type Communications (MTC) allows machines to transfer data with almost no human intervention. In MTC, power saving is one of the most important issues. In the meantime, the 3rd Generation Partnership Project (3GPP) proposes Discontinuous Reception (DRX) mechanism to allow user equipments (UEs) to receive data only at specified time slots and turn off the radio module at other time slots. Unfortunately, current DRX mechanism is designed for normal usage of mobile users, not for MTC. In this paper, we proposes Optimistic DRX (ODRX) mechanism to allow more sleep periods for MTC devices. To allow more sleep periods, ODRX considers to release the RRC connection and re-establish the connection when the MTC device is paged. We propose analytical and simulation models for ODRX, and compare with the standard DRX through simulation experiments. The results show that, compared to standard DRX, significant extra power can be saved by sacrificing little extra wake up latency.