The limit for the number of people in a video conference is different according to different initiators. 

1.If you are an organization user: DingTalk provide free video conference that can holds up to 302 people with no time limit. Please note, 302 is the maximum supported number of people in a video conference now.

2.If you are an individual user who has not joined any organization: Currently only 30 people are supported for video conferences. It is recommended that you join an organization or create an organization. After joining the organization, you can initiate video conference that contains up to 302 parties.