I am studying in here X visa. Can i invite my children here s1 or s2. How to take a invitation?

Yes, they can appy for S1 or S2. You need to send them the invitation letter and copy of you passport information page and valid X2 or resident permit for X1. By the way, they need to provide their date of birth for the applications too. The invitation letter should include the following information:

1. invitee's informaion: name, sex and when to arrive
2. visiting information: why they come, when they arrive, where to stay, how long they stay, the relationship with you, who bears the expenditure.
3. inviter's information: name, phone number, address and signature.