  Context. The eclipsing close binary UU Cas is an interacting massive
double-periodic system with a gainer star partly hidden in an accretion disk.
Aims. In order to study the physics of the accretion process in greater detail,
along with the structure and dynamics of the circumstellar matter in the
system, we supplement our previous results obtained from photometry with an
analysis of the spectra of UU Cas. Methods. We collected all available spectra
used in previous publications on UU Cas and we acquired new ones. The method of
disentangling was applied to this set of spectra spanning the years 2008-2021.
The orbital parameters were disentangled and a fit of the separated component
spectra by synthetic ones has been used to determine the physical parameters of
the component stars. We compared the results to models of the evolution of
interacting binaries. Results. We found that in addition to the dominant role
of the donor star and a weak contribution of the gainer, the line profiles are
strongly influenced by the circumstellar matter. The absorption lines reveal a
presence of a disk wind emanating above the orbital plane. The variability of
H{\alpha} emission yields evidence of changes in the structure of the
circumstellar matter on a timescale of several orbital periods.
