Conductor API participant.remove not work.

[hhmmdd]

I have created a new conference "666hualu" and added a new participant "luhj" successfully, but participant.remove return error: Invalid parameter

conferencefactory.switchboard: Level="WARN" Event="An API request could not be processed." Command="MCU=participant.remove, TSMCU=participant.remove" Conference_name="666hualu" Detail="<Fault 201: 'error="Invalid parameter"'>" Conference_bridge_conference_name="666hualu" Participant_name="luhj" Participant_protocol="sip" Participant_type="ad_hoc" Xmlrpc_parameters="{'authenticationPassword': u'hidden', 'conferenceName': u'666hualu', 'participantName': u'luhj', 'factory_source_ip': '192.168.13.123', 'participantType': u'ad_hoc', 'factory_request_address': '192.168.11.44', 'participantProtocol': u'sip', 'authenti..." UTCTime="2016-03-31 11:18:26,877"

I have no idea which parameter is invalid.