Mr. wong, generally speaking, it is hard for you to get a visa which permits you to stay in China for half a year continuousely, even though you get a multiple entry visa, you have to exit China when the stay duration of each entry is up. The visa can only be extended for 2 times, in total, it is 90 days stay duration in China. If you go to China to be in hospital, or have relatives in China, you can get a visa with a long stay duration.