  Dynamical Chern-Simons (DCS) gravity, a typical parity-violating
gravitational theory, modifies both the generation and propagation of
gravitational waves from general relativity (GR). In this work, we derive the
gravitational waveform radiated from a binary black hole system with eccentric
orbits under the spin-aligned assumption in the DCS theory. Compared with GR,
DCS modification enters the second-order post-Newtonian (2PN) approximation,
affecting the spin-spin coupling and monopole-quadrupole coupling of binary
motion. This modification produces an extra precession rate of periastron. This
effect modulates the scalar and gravitational waveform through a quite low
frequency. Additionally, the dissipation of conserved quantities results in the
secular evolution of the semimajor axis and the eccentricity of binary orbits.
Finally, the frequency-domain waveform is given in the post-circular scheme,
requiring the initial eccentricity to be $\lesssim0.3$. This ready-to-use
template will benefit the signal searches and improve the future constraint on
DCS theory.
