Atul,
First to all, this FM (gui_upload) is obsolete, use the method cl_gui_frontend_services=>gui_upload.
Second, you need split values recovered from data_tab into a new itab, like this:
REPORT z_test TYPES: BEGIN OF ytab, sno TYPE string, name TYPE string, gender TYPE string, END OF ytab. DATA: t_up TYPE STANDARD TABLE OF string WITH HEADER LINE, itab TYPE TABLE OF ytab. CALL METHOD cl_gui_frontend_services=>gui_upload EXPORTING filename = path filetype = 'ASC' has_field_separator = ',' CHANGING data_tab = t_up[] IF NOT sy-subrc IS INITIAL. " Message here ENDIF. LOOP AT t_up. SPLIT t_up AT ',' INTO itab-sno itab-name itab-gender. APPEND itab. ENDLOOP.