With GUI, I can select the poppler/cairo option instead of internal importing in the dialog when opening a pdf file. How can I select this option with command line? I want to batch convert pdf files to emf files. Following command can work except the poppler/cairo option issue.
inkscape -f test.pdf --export-emf=test1.emf

Welcome @deepbluesea to the Inkscape forum.
Well, I still do struggle with the command line support in Inkscape...
probably you can't set this option... ...at least I don't know how...

Maybe you could do it in a two step process:
1. use a standalone version of Poppler for Windows to convert PDF to SVG
http://blog.alivate.com.au/poppler-windows/

2. use Inkscape (option -z without GUI) to convert SVG to EMF

It seems to convert something but I cannot tell whether the output is always correct.
I never understood what EMF is good for...
Maybe there are converters which can convert PDF to EMF in a single step?

Does the info here help?
https://bugs.launchpad.net/inkscape/+bug/1506043

@theozh, thanks for the info although it is not a perfect solution on my case.
@Moini, I noticed the bug but it seemed a coding case. There is no importing option or preference for importing pdf in command line.

Correct. It doesn't work at the moment - but it might, wenn https://bugs.launchpad.net/inkscape/+bug/1507740 is fixed (then it will load the settings from your preferences file).