I want to create a wirless network within one kilometer range thre are 20 pc how to create?

Unless you have lots of money the range is far to long. even with a good home wirless router you will be lucky to get more than 50 metres

That's an industrial application requiring a kit far more capable than what you can find at Office Depot. You'll need to call in the big boys and have them generate a proposal for you Start with Siemens or Cisco. They both have the tech staff you need. Oh - and have your (big) checkbook handy. Unlike this forum - they are not free - or cheap

i would suggest at least 2 routers or even maybe 3 so that connections are not lost....and the routers wit the most distance. double check on where u buy ur router, they SHOULD be able to tell which router best suits ur need and its just a matter of setting it up

You can do it but you'll need lots of kit. the easiest way would be a fibre optic if they _must_ be connected, or two seperate internet connections with static IPs and then just use virtual drives and servers to juggle connections with good switches for security and directing traffic Regards