Thanks a lot for your advises.

As your reply that means my code as below
not be able to use for soap message.
Is correct ?. Then I have to use soap structure
instead QDomDocument. Please advises.

QDomDocument doc("");
QDomElement sub01 = doc.createElement("Control xmlns=''");
doc.appendChild(sub01);

// TransactionType
QDomElement tag01 = doc.createElement("TT");
sub01.appendChild(tag01);
QDomText _tag01 = doc.createTextNode("100");
tag01.appendChild(_tag01);

// TransactionReverse
QDomElement tag02 = doc.createElement("TR");
sub01.appendChild(tag02);
QDomText _tag02 = doc.createTextNode("O01");
tag02.appendChild(_tag02);

// TransactionEvent
QDomElement tag03 = doc.createElement("TE");
sub01.appendChild(tag03);
QDomText _tag03 = doc.createTextNode("ACK");
tag03.appendChild(_tag03);

QString xmlRequest = doc.toString(); //

The got the result as

<TT>100</TT>
<TR>001</TR>
<TE>ACK</TE>