Thank you @Raghavendran S for your reply~
The writer I am using is a common writer I created by clicking Add Writer button in the toolbar.
I set the format parameter to Microsoft Word and specified the saving location.
The whole thing I want to do is reading attributes from a ArcGIS mdb file, and then exporting these attributes to a Word table.
To achieve that, I used a ArcGIS mdb reader to extract attributes, and I used a MSWordStyler to convert all the attributes to table format,
I used a Microsoft Word writer to generate a document and store the content.It was so simple that it should have succeeded, however I got a issue at last.
I asked my colleague for help and I ran my workspace in his PC. The workspace behaved normally which is out of my expections. After consulting to my colleague, I finally figured it out that the MSWordStyler transformer is incompatible with FME Desktop 2019, and is compatible with FME Desktop 2018. I'm not sure my hypothe sis is right or not.