According to the Gensim Word2Vec, I can use the word2vec model in gensim package to calculate the similarity between 2 words.
e.g.
trained_model.simi
There are extensions of Word2Vec intended to solve the problem of comparing longer pieces of text like phrases or sentences. One of them is paragraph2vec or doc2vec.
"Distributed Representations of Sentences and Documents" http://cs.stanford.edu/~quocle/paragraph_vector.pdf
http://rare-technologies.com/doc2vec-tutorial/