Can anyone suggest me textbook or material to study about system of partial differential equations?
I'm working in the finite element method and I want to learn how the finite element technique works in the system of PDE. Any suggestions for materials would be appreciated.
Well, I guess you are referring to the system of PDEs such as Stokes or Navier Stokes equations. The FEM that is applied here is referred to as Mixed FEM. The book, "The Mathematical Theory of FEM" by Brenner and Scott gives a general overview of the system and then depending on your problem you can delve into some specific research papers.