Does the agent who handles Canadian temporary resident visit (business visit) visa need certain intermediary qualifications?

Agency is not mandatory. You can find someone to do it for you or you can do it yourself.

If you are looking for an agent, there are two major categories of agents accepted by the Canadian government, which are divided into paid categories and non-charged categories.

If the agent is free of charge, it can be anyone, your relatives, friends, etc.

If the agent is paid, he must be a registered immigration consultant or a registered lawyer or notary public with the Canadian Consultants Regulatory Agency.

The list of registered legal immigration consultants can be found at the Canadian Immigration Consultants Regulatory Agency.

This qualification has nothing to do with whether you have intermediary qualifications in China. In other words, the Canadian government only recognizes immigration consultants registered in Canada and has nothing to do with domestic affairs.