Abstract: Quantum discord is an important concept of quantum information，which is used to evaluate quantum correlation among systems and performs more accurately than quantum entanglement. In this paper，the concept of quantum discord，its recent developments and applications are introduced. By considering the transverse field Ising system as an example，a method to calculate quantum discord is elaborated. Thereby the system's quantum discord is obtained and a three - dimensional image characterizing the features of quantum discord is plotted.

Key words: quantum discord, quantum correlation, density matrix, transverse field Ising system