"can you show me the best power supply circuit for MCS51 system?"

No.
Without far more detail of precisely what this "MCS51 system" consists of, how much power does it need, are there any sensitive analogue parts, what power source is available, what other constraints & requirements exists in your application, etc, etc, etc, etc, ... it is completely impossible to even guess what the best PSU might be.

Even if we did have all the info, there may well still not be a single best solution - most likely there will be a number of options, each with its own advantages & disadvantages.

Engineering very seldom has "right" answers - just appropriate solutions!