  We present the construction of Maxwell's equal area law for the Guass-Bonnet
AdS black holes in $d=5,6$ and third order Lovelock AdS black holes in $d=7,8$.
The equal area law can be used to find the number and location of the points of
intersection in the plots of Gibbs free energy, so that we can get the
thermodynamically preferred solution which corresponds to the first order phase
transition. We obtain the radius of the small and large black holes in the
phase transition which share the same Gibbs free energy. The case with two
critical points is explored in much more details. The latent heat is also
studied.
