  We calculate the complete $T$-matrices of pion-nucleon ($\pi N$) scattering
to the third order in heavy baryon SU(3) chiral perturbation theory. The baryon
mass in the chiral limit $M_0$ and the low-energy constants are determined by
fitting to phase shifts of $\pi N$ and the experimental octet-baryon masses
simultaneously. By using these constants, we obtain the pion-nucleon sigma
terms, $\sigma_{\pi N}=(34.57\pm 11.85)$ MeV. We also find that a very small
strangeness content of the proton, $y \simeq 0$. The scattering lengths and the
scattering volumes are predicted, which turn out to be in good agreement with
those of other approaches and the available experiment data. The contributions
from the third-order amplitudes are discussed in detail. We find that the
contributions from the internal kaon lines of one-loop diagrams and the
counterterms of the third order are sizeable. In addition, the issue of
convergence is also discussed.

Nuclear Theory;High Energy Physics - Phenomenology