https://www.researchgate.net/profile/Matej_Velicky/publication/255757138_On_the_stability_of_the_silversilver_sulfate_reference_electrode/links/54b1b4480cf220c63cd12905.pdf

Consider it only if you need a Cl- free reference electrode. 

Article On the stability of the silver/silver sulfate reference electrode

 You don't indicate why you can't use a Ag/AgCl reference electrode.  Will slight traces of Cl- from the liquid junction affect your results?  In such a case, a double liquid junction could be used.  However, if you want to use the Ag/AgSO4 reference electrode directly in your sample solution, then the SO4= concentration must be maintained in order to fix the reference electrode potential.

@Durst...Because the pH limit for Ag/AgCl electrode is pH 0-14, but I wanna use ref. electrode in negative pH. Also slight traces of Cl- will affect my reaction media.

Yes, John, I am that Richard Durst.  However, although I (actually my students) dabbled in developing immunoassay-based biosensors, I would hardly call myself an expert.  But thank you for the compliment.

Silver sulfate electrode is not "the best" electrode to be used. I imagine that you will work with the same electrolyte inside and outside of your electrode and so eliminate the junction potential. This is the unique reason than I can imagine for this choice.

You can form silver sulfite (Ag2SO4) on a silver wire imposing externally an adequate potential for the oxidation of the silver wire. A insoluble Ag2SO4 will be formed on the wire, but I have no information about the stability of this electrode. 

The solubility of Ag2SO4 relatively elevated (Ks = 7.7 x 10-5) and this is not so favorable for stability.

 Best regards,

Lucio