In modern Chinese, interrogative sentences are transformed from indicative sentences. At first, this paper gives the classification of modern Chinese interrogative sentences and their transformation from indicative sentences. Then we analyze the querying focus and point out that the querying focus is an abstract of a component of an indicative sentence and so an interrogative sentence is formed. Adopting the idea of the structured meaning approach, we present the semantics of modern Chinese interrogative sentences and their formal representations basing on the functor. All kinds of Chinese interrogative sentences including “NP+ne” and “VP+ne” are analyzed. Why we start from QF to study interrogative sentences is also discussed.