It is safe - as long as you go to a trusted tattoo artist/shop. Always ask to see the tattoist's work beforehand, preferably live (in the flesh), or if that's not possible then at least photos of end results. Ask if you can observe his/her technique while they tattoo somebody else, and check if everything is brand new/sterilized. Everything needs to be taken out of sterilization bags prior to use, and ideally the artist should be wearing gloves, and not smoking.
Once you feel comfortable, you can discuss a price. Most good tattoo artists in China will charge per hour, but they can give you a rough estimate of how long it will take beforehand. If done in this way, any 'top-ups' for colour or thickness should be free.

Don't make the same mistake I did and go for a 'friend of a friend' who had his own studio. Super-cheap tattoo (200 RMB, should have cost 800), shit quality, crap finish, and it will stay with me forever.

I had mine done in Guilin and I absolutely LOVE it.  5 years later, I dont seem to have picked up anything....