My company name going to change soon. Is it necessary to amend the name of our company for all old preliminary notices and send the new notice to all the parties?
Yes, this seems like a prudent action. Of course, there may be many other significant legal issues which can arise from a "name change" in California (e.g., contractor's license law issues) -- especially if the corporate entity or business form is changing as well. You should consult with an experienced construction attorney to make sure you have thought through all the possible issues.