How to protect the patented formula, what others think of my formula, improve it on my basis, and then develop new products, is this an infringement?

We need to see the improvement, and to what extent. If it is improved, every feature (composition and parts) defined in your patent claim (independent claim, usually claim 1) is still in his improved new product, and if so, it is still infringement; But if some features are gone and there is no equivalent substitute, it is not infringement, and even he can apply for a patent for improvement.