  Within a nuclear model that the deuteron has NN and \pi NN components, we
derive convolution formula for investigating the Drell-Yan process in
proton-deuteron (pd) reactions. The contribution from the \pi NN component is
expressed in terms of a pion momentum distribution that depends sensitively on
the \pi NN form factor. With a \pi NN form factor determined by fitting the \pi
N scattering data up to invariant mass W = 1.3 GeV, we find that the
pion-exchange and nucleon Fermi-motion effects can change significantly the
ratios between the proton-deuteron and proton-proton Drell-Yan cross sections,
R_{pd/pp} = \sigma^{pd}/(2\sigma^{pp}), in the region where the partons emitted
from the target deuteron are in the Bjorken x_2 > 0.4 region. The calculated
ratios R_{pd/pp} at 800 GeV agree with the available data. Predictions at 120
GeV for analyzing the forthcoming data from Fermilab are presented.
