The requirement is to send list of results to eamil with an attached excel file, for that i used "pzMSOGenerateExcelAndSaveToWorkFileAttachment" activity to convert excel into encoded formate and sending the same as an attachment to the email but in PEGA date format i.e 20140101 is sending as it is to the excel. Please suggest How can I fulfil this requirement.
I believe you are re-using some OOTB activities to generate EXCEL files ; these OOTB activities were designed as utilities for specific PRPC functions in particular wizards/accelerators.
If they don't do quite what you want to do: you might have to develop your own Activity for this purpose: under the covers the Activity uses a (rebadged) version of the Apache POI library - which you could leverage directly.
OR: if your requirements are simply to produce a file which can be viewed in EXCEL; you have a number of other options:
1. Use the OOTB PRPC Report Mechanism: this has already an option 'Export To Excel'. (actually this exports to a subset of the HTML format, which EXCEL will render as a single-sheet Excel page).