Using dissipative particle dynamics (DPD) to model a oil-water interface in lammps，there are conservative，dissipative，and random forces in DPD model，Can I calculate the interaction between oil and water in this model, such as Coulombic，vdW and Lennard-Jones interactions？Or is the conservative force the sum of these interactions？

There are many “flavors” of DPD, each with their own derivation and potential functions.

Pair style dpd implements the original DPD model by Groot and Warren 1997. The potential function for that pair style is exactly as shown in the documentation.

There is no explicit coulomb and lennard-jones in that model. If you need more information about the model itself and how to represent different systems, then this is not really a LAMMPS problem, but more a “theoretical problem”, i.e. something for which you need to study the published literature and relevant textbooks to learn from others that have already done similar simulations.