There are several ways not to lose your trademark in China. The first is free and 100% bullet-proof: you must be sure that no one knows your trademark in China. You shouldn't accept clients from China, advertise, sell, talk to anyone connected with China and so on.
If you run an offline business it's not so difficult. You won't care about your trademark in China and it's unlikely that you lose it there; and even if you do, well... You won't ever get to know this.
If this sounds difficult, since you have clients/suppliers/visitors from China, my advice will be - register your trademark. It costs US$399 for 10 years in Bonamark. You can't imagine how important it is.
We had a case in which our client had a trademark, let's imagine that the trademark was "TRADE MARK". He had a partner in China, who manufactured some products under our clients' mark. They worked together for several years and then suddenly our client got to know that his trademark was registered by his supplier! The supplier registered "TRADE", "MARK", "TRADE MARK", "TRADEMARK", "MARK TRADE" and finally "MARKTRADE".
It took a year and US$50.000 to cancel some of the trademarks and the process is not over yet.
So if you sell your products in China or plan to sell within next 3 years - Apply For Your Mark.
If you were attentive, you would have noticed that I mentioned 3 ways. Thus, what is the last way?
The last way will be to order a Trademark Watch. It costs slightly less (around US$180/year) and we will watch for any similar trademark in China. If it appears, you will be able to oppose it and prevent it from registering.
The conclusion is: if you work with China and want to have your trademark safe, register it.
International Trademark Search
Check if your trademark is available for registration.
International Trademark Registration
Protecting your trademark is the most important investment you can make.
International Trademark Watch
Be informed of recently applied similar or identical trademarks.