This thesis studies the meromorphic functional solutions of Fermat type functional equation and proves the following results by the value distribution theory of meromorphic function and normal families theory·For n>3, we give a new proof of the result there do not exist two nonconstant entire functions f(z) and g(z) that satisfy f~n(z)+g~n(z)=1.·Let f(z), g(z), h(z) be meromorphic functions in the plane of order ρ_f<1/2.If f(z), g(z), h(z) have at most one common simple pole, then there do not exist three nonconstant meromorphic functions f(z), g(z), and h(z) that satisfy f~7(z)+g~7(z)+h~7(z)=1.·For n≥13, there do not exist three nonconstant meromorphic functions f(z), g(z), and h(z) that satisfy f~n(z)+g~6(z)+h~6(z)= z. |