I tried to see from China's point of view why China did not participate in carrying out economic sanctions like America, Britain, Australia, Japan etc. It turned out that it was because they thought that what America was doing was illegal because it was based on a unilateral decision. He even said that since 2011 America has imposed sanctions on Russia 100 times, perhaps because of that Russia is still stable even though it is limited by several countries because they feel they are used to it.
And also, it's simple that they're allied with Russia.
An ally won't do sanction if they've been partners for a long time. But as well as the competition for these superpowers has been there for a long time.
The advantage is with China that they'd bring help to the economy of Russia.