My video is delete by mistake

I take it, you have already checked the Recently Deleted album? This is the only place where Photos is saving deleted items for up to thirty days. (If you're missing photos or videos in the Photos app - Apple Support ) If the video is no longer in Recently Deleted, you have to fall back on the backups you made before your video got deleted. Try to find a backup you made while the video has still been around and restore the iPhone from this backup. See: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Not all backups will include the photos and videos. Your regular iCloud backup will not include any items that are synced with iCloud. If you have been using iCloud Photos, the videos will not be included in your iCloud backup and you have to find a backup you made on a computer.