EPI with sub-second sampling rates is essential for fMRI to increase tSNR and filter out physiological noise. Simultaneous multiple slice (SMS)-EPI using multi-band (MB) slice excitation has been successfully applied to acquire whole brain fMRI data in < 1s. However, the reconstruction of SMS-EPI remains in separate 2D/1D GRAPPA or partial 3D GRAPPA in ky-kz’-kx domains. To further increase acquisition speed, TR< 500ms, higher k-space dimensional GRAPPA can be used to improve reconstruction performance, e.g. increase SNR and decrease aliasing artifacts. To meet this need we developed a full 3D ky-kz-kx GRAPPA reconstruction for SMS-EPI validated it by simulation and experiment at 7T.