The Mid-Pleistocene Climatic Transition (MPT) is one of the most significant characteristics of the Quaternary climatic changes. MPT means the dominant global climate cycle changed from 40 ka to 100 ka during the mid-Pleistocene with higher amplitude. The classical Milankovitch hypothesis can't give a satisfactory explanation for the cause of the MPT and the predominant 100 ka cycle in climate records because of the discrepancy between solar insolation and climate records, especially the unmatched change amplitudes of them. This paper introduce the progresses of this question, such as the time of the MPT, the re-examination on 100 ka cycle in paleoclimatic records, and the role of non-insolation factors, such as the ice sheets, green house gas, ice-sheet's underlying substrate, orbital plane inclination, and tectonic uplift.