The spatial absolute phase information is important in various stages of MRI scanning, such as parallel image reconstruction, the combination of MR image or MR spectroscopy from each element of multiple receivers and exploration of new contrast and biomarker. Currently, the absolute phase of a transmit field can only be roughly estimated as half of the transceiver phase. This method is not only inaccurate but also not applicable for a transceiver coil. Thus, the accurate estimation of the absolute phase for an arbitrary RF coil system is an unsolved problem and an unmet need of the MR society. Here we propose a new approach to solve this old problem.