I have a sentence:
The Theorem states the properties of the solution of the model.
Too many "the" here... Is there anything wrong in grammar?
You're relying too heavily on the phrase "of the" to attribute nouns to other nouns in terms of ownership.
You can add verbs to this sentence to help remove the "thes" if you don't like the sentence now. However, nothing is technically wrong with it. The verbs will perform the attributing for you, instead of "of."
The Theorem states properties exhibited by the model's solution.
I don't know if "exhibited" is the right verb here. You'll have to analyze your own context to use the correct word.
You can also attribute these nouns to their owners or creators via possession to further eliminate usage of "the." For example:
Einstein's Theorem states properties exhibited by his model's solution.
Einstein's Theorem states the properties of his solution of the model.
Again, you'll have to analyze your own context to figure out what nouns need to be attributed to whom.
those THEs can be replaced by any other determinants too.