Threshold graphs are generated from one node by repeatedly adding a node that links to all existing nodes or adding a node without links. In the weighted threshold graph, we add a new node in step i, which is linked to all existing nodes by a link of weight w_i . In this work, we consider the set A_N that contains all Laplacian matrices of weighted threshold graphs of order N. We show that A_N forms a commutative algebra. Using this, we find a common basis of eigenvectors for the matrices in A_N . It follows that the eigenvalues of each matrix in A_N can be represented as a linear transformation of the link weights. In addition, we prove that, if there are just three or fewer different weights, two weighted threshold graphs with the same Laplacian spectrum must be isomorphic.