Due　to　its　potential　application　in　signal　analysis　and　image　processing,　quaternionic　Fourier　analysis　has　received　increasing　attention.　This　paper　addresses　quaternionic　subspace　Gabor　frames　under　the　condition　that　the　products　of　time-frequency　shift　parameters　are　rational　numbers.　We　characterize　subspace　quaternionic　Gabor　frames　in　terms　of　quaternionic　Zak　transformation　matrices.　For　an　arbitrary　subspace　Gabor　frame,　we　give　a　parametric　expression　of　its　Gabor　duals　of　type　I　and　type　II,　and　characterize　the　uniqueness　Gabor　duals　of　type　I　and　type　II.　And　as　an　application,　given　a　Gabor　frame　for　the　whole　space　L2(R2,H)\documentclass[12pt]{minimal}　\usepackage{amsmath}　\usepackage{wasysym}　\usepackage{amsfonts}　\usepackage{amssymb}　\usepackage{amsbsy}　\usepackage{mathrsfs}　\usepackage{upgreek}　\setlength{\oddsidemargin}{-69pt}　\begin{document}$$L＜^＞{2}({\mathbb　{R}}＜^＞{2},\,{\mathbb　{H}})$$\end{document},　we　give　a　parametric　expression　of　its　all　Gabor　duals,　and　derive　its　unique　Gabor　dual　of　type　II.　Some　examples　are　also　provided.