Hi,Do I need Chinese Visa?

I am planning to visit Hong Kong from India transiting through Guangzhou airport by train. I am planning to take Bus Line 3 from Airport South station in Guangzhou airport to reach Guangzhou East Station to board the train to Hong Kong. I am planning to follow same route on my way back from Hong Kong to Guangzhou airport for the flight to Melbourne. As I am just transiting, my stay in China would be less than 24 hours.