Is Mac OS Virus free?

It is pure fiction that mac os is virus free. This is because there are so much fewer people using a mac, only about 10%?? Thus there is only 1/10 chance of people telling you that their mac have encountered a virus and 9/10 chance that people will tell you that their PC have encountered a virus. Thus most prob you only hear about PC getting viruses because it is so common as there are so many people using it. One exameple is like car accidents you see taxis involved in most of them because there are so many taxis in the country while you seldom see mercs involved in car accidents. That does not mean that mercs cars are immuned to car accident it is just so rare because few people drive them compared to taxis.

I also heard that Mac OS is virus free from long time ago, but recently(if forget what tech, news site) report that there a Mac OS antivirus release to market coz seem like more and more people using mac and someone/more and more virus creator try to create virus to Mac OS

I don't think so. many people hold that opinion only because Windows is more widely used than Macintosh OS in the world and has become the study object of many malicious hackers.