Why encounter this error when I attempt to get the product of Interferogram Formation?

I used a pair of SLC from RADARSAT 2
the memory of my PC is 8G
The same consequence occured when I use the ERS-2 N1

Impossible to say due to lack of information, please clarify. Guidelines for problem reporting are here:

Toolbox: version S1 Toolbox
operating system:WIN7 64BIT
amount of RAM :8G
full name of the product:A pair of Vancouver_R2_FineQuad15_Frame1_SLC
the exact processing steps :Interferogram Formation
I can’t accomplish the processing of the Interferogram,and don’t know why.I am eager to get the results.

Before interferogram-formation you need to coregister the images - please consult the tutorials.

http://step.esa.int/main/doc/tutorials/sentinel-1-toolbox-tutorials/

I have done the job step by step according to the tutorials,includng the coregistering.Then the error of warning appeared.I’ll try again.thank you all the same.

After creating your coregistered stack, it looks like you apply a speckle filter. Speckle filtering is only done on the intensity so your result will not have complex values. You need complex data for an interferogram.
Don’t apply speckle filtering for InSAR.

Um,I see.What you’ve pointed is so important.Thanks for your patient reply.Before you reply to me,I’ve got the consequence of interferogram-formation.I didn’t set the Parameters instead of changing it.But I know about more about st1bx.Thanks again for your job.