It depends on which property you want to deal with: mass/inertia? axial, bending or torsional stifness?, thermal conductivity?, etc.

Moreover do you mean a cylinder with different thickness (i.e. coating, core, etc.) or two or more cylinders in a series (axially aligned)?  

Pier Thanks for your response.

I am talking about Cylinder with Different Thickness and Material (ref .jpj attached).

I want find the equivalent cylinder with single Young's Modulus(Equivalent) and Poisson's Ratio(Equivalent)

Structural properties depend on integrals over the section (i.e. axial stifness is E*A, bending stifness is E*I and so on). So, an equivalent structure must have the same stifness properties. You can impose equal the expression of the compund cylinder and the equivalent cylinder. Just for example, in case of axial stifness you have:

Stifness of the compound = E1*A1+E2*A2

Stifness of the equivalent cylinder = Eeq*Aeq

Actually you have to set equal the two stifness and solve for Eeq. Consider Aeq as a free parameter. If you add the same equations written in terms of bending moment you can folve for Aeq as well.

Thank you Pier  

Your Answer is helpful