Abstract: The astronomical theory of ice age provide an update solution to Quaternary glacial- interglacial cycles based on the long-term variations of three earth’s orbital parameters, eccentricity, obliquity and precession. This theory had been under modification over one hundred years since it was suggested by Adlhemar in 1842, developed by Croll and finished by Milankovitch in 1941. Since 1960s, numerous geological records from sea, loess and ice core have been exhibiting the three different cycles of 100kyr, 41kyr and 21kyr, demonstrating the validity of the theory, and meanwhile, brought some revision to the theory. However, there are still a lot of brainteaser between the geological records and the theory that needs to resolve. The calculation by A. Berger indicates that the curve of insolation controlled by the three orbital parameters exhibits similar changes for at least past 6Ma, but the curves of geological records present piecewise response. For example, obliquity of 41kyr cycle was dominant between 5.3~1.4Ma; Onset of the major northern hemispheric glaciation started up at approximately 2.7 Ma; 100kyr periodicity of eccentricity substituted 41kyr periodicity of obliquity around 0.8 Ma, which is called the Event of Middle Pleistocene Transition. In addition, why the most prominent glacial–interglacial transition occurred at time of minimal eccentricity of Stage-11 and Holocene; How to explain the slow transitions from interglacial to glacial and the quick transition from glacial to interglacial in 100kyr cycles, and so on. Those questions associated with the response mechanism of the complex earth system to the orbital forcing, and were warmly discussed in the past decade.