Currently I have design my circuit and now I want to purchase the component, can someone teach me which one is correct?

For example resistor have a lot of type , let take the example the fix value resistor, there are 1/4 W , 1/2W , 1W. How to select these component?

 

With no knowledge of the circuit, it's kind of hard to be definite about the resistor wattages. The power dissipated in a resistor is equal to the square of the current times the resistance, so you can use that formula to see if you need resistors larger than 1/4 watt.

 

Derate resistor power by half because a resistor operating at its rated power is hot enough to burn you or melt plastic insulation.
A resistor operating at its power rating will overheat if it is enclosed because it needs free flowing ambient air at room temperature.

 

Of course, heat is a relative quantity. Even in a medium amplifier, the current amplifier resistors will be too hot for you to touch but hopefully not hot enough to burn your project.