@Chen Ta,
Quote:Is there any meaning difference between below sentences ? For me ... it looks like both of the sentences are correct... is any difference in the sentence meaning?
I agree with you that the meaning doesn't change any. The comma is a matter of "style" (aka punctuation). This could stand alone, as it's own sentence: "The child cried loudly." The rest is elaboration on the circumstances, and is not necessary to convey the basic idea of the sentence. In that sense, I guess it is a "subordinate clause" or something like that---A grammar book would tell you, but I'm not looking at one of those.
The comma, as used here, is designed to indicate a slight pause in the way it would be related if spoken. It may also be deemed to be "required" to offset what I'm calling the "subordinate clause," technically speaking, but I'm not sure about that. I never memorized grammatical terminology (and I never will).