  In this paper we use the equation of state (EOS) of 2+1 flavors
Nambu-Jona-Lasinio (NJL) model to study the structure of compact stars. To
avoid the ultraviolet divergence, we employ the proper-time regularization
(PTR) with an ultraviolet cutoff. For comparison, we fix three sets of
parameters, where the constraints of chemical equilibrium and electric charge
neutrality conditions are taken into consideration. With a certain
interpolation method in the crossover region, we construct three corresponding
hybrid EOSs but find that the maximum masses of hybrid stars in the three
different cases don't differ too much. It should be pointed out that, the
results we get are in accordance with the recent astro-observation PSR
J0348+0432, PSR J1614-2230, PSR J1946+3417.
