توی Qt 5 این کار رو انجام دادم و جواب داد این راهنمایی هست که واسه خودم نوشته بودم :
1. Open C:\Qt\Qt5.3.2\5.3\Src\qtbase\src\plugins\sqldriver s\ibase\ibase.pro
2.Edit ibase.pro :
TARGET = qsqlibase
INCLUDEPATH += "D:\\Development\\Firebird\\Server\\Firebird25_32\ \include"
LIBS += "D:\\Development\\Firebird\\Server\\Firebird25_32\ \lib\\fbclient_ms.lib"
SOURCES = main.cpp
OTHER_FILES += ibase.json
include(../../../sql/drivers/ibase/qsql_ibase.pri)
PLUGIN_CLASS_NAME = QIBaseDriverPlugin
include(../qsqldriverbase.pri)
3.Build Release & Debug
4.Copy qsqlibase.dll & qsqlibased.dll from C:\plugins\sqldrivers\ to C:\Qt\Qt5.3.2\5.3\mingw482_32\plugins\sqldrivers