1, the chapter arrangement is different. The last chapter of the second volume of the fifth edition of Differential Equations is arranged to the last chapter of the first volume of the sixth edition. 2. The exercises are different. But on the whole, we seldom do book exercises in class. Therefore, in general, the teaching content of the whole book has not changed, except that the postgraduate entrance examination took the Tongji Fifth Edition. If you want to take the postgraduate entrance examination, it is recommended to use the fifth edition.