  We study deformation of Courant pairs with a commutative algebra base. We
consider the deformation cohomology bi-complex and describe a universal
infinitesimal deformation. In a sequel, we formulate an extension of a given
deformation of a Courant pair to another with extended base. This leads to
describe the obstruction in extending a given deformation. We also discuss
about the construction of versal deformation of Courant pairs. As an
application, we explicitly compute universal infinitesimal deformation of
Poisson algebra structures
