I have found that Qt Creator 2.3.0 can't automatically take toolchain for arm, but the previous versions can do that. When i get into the code. I found that from Qt Creator 2.3.0 onwards the function 'static QList<Abi> abiOf(const QByteArray &data)' in file 'src/plugins/projectexplorer/abi.cpp' has been modified. I found the reason also. In the previous version the QT version ABI and toolchain are showing as 'arm-linux-generic-elf-32'. But from 2.3.0 onwards Qt version ABI showing as 'arm-unix-generic-elf-32' and toolchain ABI as 'arm-linux-generic-elf-32' and so its mismatching. The probem is because of deciding the OS type based on ELF flag. the build is having the value 97 for ARM which was never matched with any condition in abiOf() function and it is defaulted to Unix os. I think its a bug because this alters the default behaviour of Qt Creator