Hi,
Is there any grammatical mistake in "Compared with India,the situation is different in China "?
I wouldn't say the grammar is wrong. However, the sentence sound odd. It's probably because of the use of 'compared' and 'different' in the same sentence.
Another problem is that, in your original sentence, you seem to be comparing 'India' to 'the situation in China', and these are not two comparable things.
I'd say something like "The situation in India is different than that in China." This makes it obvious that we are comparing, without explicitly using the word 'compared'.
Best wishes, Clive