Abstract: Twin effect is resolved by using two-dimensional plot in the Minkowski＇ s four-dimensional space time, it also comes to a quantitative analysis of the earthmen＇ s age jump caused by the isochrone＇ s jump which is the consequence of spacecraft＇ turning in particular. Then there comes to an absolute conclusion of those who came through the accelerated movement of the spacecraft are younger than their twins who lives on the earth which is thought as an inertial system. In the end, the discussion of the results supported by the numerical calculation gives the specific observations on the spacecraft in the round trip and the whole system in two different references.

Key words: twin paradox, four-dimensional space time, Minkowski＇ s geometry, same time line jump