No, you don't require to drop the target schema, this will import the data from the source schema and add it to the target schema.
thank you for replay. but is it need to drop target schema to do imp?
To do this work, you can use Data Pump.
$ expdp directory=datapump dumpfile=scott_bkp.dmp logfile=scott_bkp.log schemas='SCOTT
$ impdp directory=datapump dumpfile=scott_bkp.dmp logfile=imp_schema.log remap_schema='SCOTT:HR'
You may learn more about Data Pump by visiting this site.