Hello, group chat contains Secured Enterprise Group, Enterprise Group, Department Group, All-hands Group and General Group, the creating rules have some difference:
[Create Secured Enterprise group/General Group]
1. Mobile DingTalk app: right upper side [+] - [New Chat];
2. DingTalk desktop client - middle up side - [Create Group Chat];
3. When you create the group, if the members you select are in one company then the group will be a Secured Enterprise Group, and if the members you select are in the different company, then the group will be a General Group.

[Create All-hands Group/Department Group]
1. You have to create an organization first, then to create All-hands Group/Department Group based on your organization. In addition, the group's super admin must be the main admin or the sub-admin who have the authority to set "Contacts", others can not create the groups;
2. All-hands Group: [DingTalk mobile app] - [Contact] -[Group Chats] - [Create]
DingTalk desktop client（https://oa.dingtalk.com）- [Contacts] - [choose the company] - [Settings] - [Creat All-hands Group];
3. Department Group：[DingTalk mobile app] -[Contacts] - [find your department] - [Edit]- [Edit] - [Department Group] - press [not created];
Admin login on desktop client admin panel-[Contact]-[Select Department] -[Edit] - [Create Group]