this is the In Progress stage screen-shot

as the picture above, when i create a new task, it automatically set to undefined stage. how it can be set to in-progress stage by default?

In order to do that, you need to set the "Related status" of your "Stage Name" to "New".

After that, the stage name of your newly created task will automatically be setted to the "Stage Name" you define as "New", in your case, "In progress"

Hi, I'm using odoo 10,
Icannot find default for new project in stage.

please help