Thanks for your advice. I will negociate with the company to see we can come up. I have two questions to confirm.
1. If I can not start the work on 10/1. H1 will be invalid, so I can not use this H1 anymore. If the company want to hire me in the future after 10/2, no matter when, I need a new H1 petition. Is it right?
2. As pjiang's advice, report the employer and request a leave. I do not know how it will affect my future green card application.
Thanks in advance again.