Dear Stubbs,
Thank you very much!
I understand how to set parameter in MDO query.
The key word is : [param.number] 
Now I can set the default value and parameter type of the parameter, and test to see the result.
about:
3. How to test the Transaction with a dynamic parameter MDO query?
How to pass the value of the dynamic parameter in the MII Transaction?
I'm testing the PCo connection. I can call the MII Transaction from PCo when the tag value changed.
The MII Transaction has a inputXML property.
How can I get the tag value from PCo (inputXML)? and then pass it to the dynamic parameter of the MDO query?
Thank you!!!!