We have a friend who wants to move from Beijing to Kunming, could anyone recommend some reliable home-moving companies to us ?

How about Ant movers? I see their moving trucks everywhere.

Beat me to it. Ant removals is the name in English. They are reliable Chinese company, I think they may be in Beijing.
If your friend is an expat on all removal expenses paid, then we have used Santa Fe with no problems.

If your friends are coming from Beijing, it might be better to find a company at that end.
If it is only a few boxes, I have heard of people using China Post.