  We construct a linear optics measurement process to determine the
entanglement measure, named \emph{I-concurrence}, of a set of $4 \times 4$
dimensional two-photon entangled pure states produced in the optical parametric
down conversion process. In our experiment, an \emph{equivalent} symmetric
projection for the two-fold copy of single subsystem (presented by L. Aolita
and F. Mintert, Phys. Rev. Lett. \textbf{97}, 050501 (2006)) can be realized by
observing the one-side two-photon coincidence without any triggering detection
on the other subsystem. Here, for the first time, we realize the measurement
for entanglement contained in bi-photon pure states by taking advantage of the
indistinguishability and the bunching effect of photons. Our method can
determine the \emph{I-concurrence} of generic high dimensional bipartite pure
states produced in parametric down conversion process.
