  The jet composition of gamma-ray bursts (GRBs), as well as how efficiently
the jet converts its energy to radiation, are long-standing problems in GRB
physics. Here, we reported a comprehensive temporal and spectral analysis of
the TeV-emitting bright GRB 190114C. Its high fluence ($\sim$
4.436$\times$10$^{-4}$ erg cm$^{-2}$) allows us to conduct the time-resolved
spectral analysis in great detail and study their variations down to a very
short time-scale ($\sim$0.1 s) while preserving a high significance. Its prompt
emission consists of three well-separated pulses. The first two main pulses
($P_1$ and $P_2$) exhibit independently strong thermal components, and starting
from the third pulse ($P_3$) and extending to the entire afterglow, the spectra
are all non-thermal, the synchrotron plus Compton up-scattering model well
interpret the observation. By combining the thermal ($P_1$ and $P_2$) and the
non-thermal ($P_3$) observations based on two different scenarios (global and
pulse properties) and following the method described in \cite{Zhang2021}, we
measure the fireball parameters and GRB radiative efficiency with little
uncertainties for this GRB. A relevantly high GRB radiative efficiency is
obtained based on both the global and pulse properties, suggesting that if GRBs
are powered by fireballs, the efficiency can be high sometimes. More
interestingly, though the observed parameters are individually different (e.g.,
the amount of mass loading $M$), the radiative efficiency obtained from $P_1$
($\eta_\gamma=36.0\pm6.5\%$) and $P_2$ ($\eta_\gamma=41.1\pm1.9\%$) is roughly
the same, which implies that the central engine of the same GRB has some common
properties.
