How long will there be a notice after the job fair?

Not necessarily if you submit your resume. Sometimes, when HR read your resume that day and thinks you are suitable, it will inform you to go for an interview tomorrow or the day after tomorrow.

Sometimes human resources are busy and need to wait patiently, but if the company really recruits talents, it won't take more than a week. If there is no interview call for a week, then you can find the next one.