In this paper, we construct a new geometric integration method which is based
on the Lie group SL(2, R) to solve the nonlinear longitudinal convective-radiativeconduction fin equation. SL(2, R)-shooting method and related algorithm to find a
high accuracy solutions are discussed. Finally, effects of thermal conductivity parameter, surface emissivity parameter, convection-conduction and radiation-conduction
parameters are illustrated on the performance of fins.