How to make a payroll system in excel so that it is very easy to compute rather than making a payroll manually...

It really depends on the complexity of your payroll. You can use the VLookup functions to calculate the tax witholdings. You can get the tax tables from the tax authorities and import them in.

But payroll is a daunting task and you would probably be better outsourcing it. There are a number of good payroll firms like ADP, Paychex and more.