I saw a lot of Thiele's equation is the past papers. But I can't find anything for it in CM1 CMP. So does it mean Thiele's equation is out of the syllabus?
Thiele's differential equation used to be part of the CT5 syllabus, but it was removed some time ago (in 2015, by the looks of things). It's not in the CM1 syllabus either, so you can ignore past paper questions on this for the purposes of your revision. The full CM1 syllabus is included in the Study Guide at the front of the CMP. Also, if you have ASET (2014 to 2017 papers), there's a grid at the front that tells you which past CT1, CT4 and CT5 paper questions are relevant to the current CM1 syllabus, going back to April 2008.