Thank you for writing, and for your interest in our program. Having an art history major is a good qualification to apply for our MPhil program, so you're a suitable applicant. But if you're interested in studying western art, it looks like your preparation is weaker than in Chinese art. If you wanted to write a thesis on 19th-century European art, for example, you might not have enough background knowledge and training to be successful. If you wanted to write on Chinese art, it looks like you do have enough background.
As you probably know, our program is an MPhil program, which is based on 2 years of research and writing to produce a master's thesis; we have very little coursework in the MPhil program, and you would work with one main supervisor. For this reason, it's important to have a solid background in your area of research before entering the program, and it's important to have a good topic agreeable to your potential supervisor.
So the next thing you should do if you're interested in applying to HKU is decide on an area of research and begin composing a research plan. This is the main element of the application, and it should explain the material you propose to study, the research questions you plan to explore, and the scholarly work that's already been done on the topic by art historians. You should send your proposal to a supervisor ahead of time for some feedback.
If you are also applying to overseas MA programs, the application process is quite different, and MA programs would give you good coursework to strengthen your knowledge of western art. Also, our MPhil program is small - just 2 or 3 students admitted per year - so it's quite competitive, whereas MA programs usually admit more students.
By the way, on your c.v. you should indicate in what city the China Academy of Art is located. We probably call it the Chinese Academy of Art in English, but there are many institutions with similar names, so I'm not sure.