Diagram is attached below..In the excited sate of P (Z=15) Why the electrone goes to 3d orbital instead of 4s….as according to energy level in multielectrone atoms 3d > 4s.....

yes ,you are very correct abot the energy order that is,energy of 3d>4s.But in case of excitation of electron the electron in the ground state in 3p orbital will go to the next higher orbital that is closest,that is 3d.
Remember we have 3d shell next to 3p so electron will be excited in this state.
An electron cannot jump to 4^th shell directly.
Remember in writing the electronic configuration of +ion we are removing electron from the last orbital and not the previous last.