  Studies of rest-frame optical emission in quasars at $z>6$ have historically
been limited by the wavelengths accessible by ground-based telescopes. The
James Webb Space Telescope (JWST) now offers the opportunity to probe this
emission deep into the reionization epoch. We report the observations of eight
quasars at $z>6.5$ using the JWST/NIRCam Wide Field Slitless Spectroscopy, as a
part of the ''A SPectroscopic survey of biased halos In the Reionization Era
(ASPIRE)" program. Our JWST spectra cover the quasars' emission between rest
frame $\sim$ 4100 and 5100 \r{A}. The profiles of these quasars' broad H$\beta$
emission lines span a FWHM from 3000 to 6000 $\rm{km~s^{-1}}$. The
H$\beta$-based virial black hole (BH) masses, ranging from 0.6 to 2.1 billion
solar masses, are generally consistent with their MgII-based BH masses. The new
measurements based on the more reliable H$\beta$ tracer thus confirm the
existence of billion solar-mass BHs in the reionization epoch. In the observed
[OIII] $\lambda\lambda$4960,5008 doublets of these luminous quasars, broad
components are more common than narrow core components
($\le~1200~\rm{km~s^{-1}}$), and only one quasar shows stronger narrow
components than broad. Two quasars exhibit significantly broad and blueshifted
[OIII] emission, thought to trace galactic-scale outflows, with median
velocities of $-610~\rm{km~s^{-1}}$ and $-1430~\rm{km~s^{-1}}$ relative to the
[CII] $158\,\mu$m line. All eight quasars show strong optical FeII emission,
and follow the Eigenvector 1 relations defined by low-redshift quasars. The
entire ASPIRE program will eventually cover 25 quasars and provide a
statistical sample for the studies of the BHs and quasar spectral properties.
