  Super-resolved angular displacement estimation is of crucial significances
for quantum information process and optical lithography. Here we report on and
experimentally demonstrate a protocol for angular displacement estimation based
on a coherent state containing orbital angular momentum. In the lossless
scenario, with using parity measurement, this protocol can theoretically
achieve 4$\ell$-fold super-resolution with quantum number $\ell$, and
shot-noise-limited sensitivity saturating the quantum Cram\'er-Rao bound.
Several realistic factors and their effects are considered, including nonideal
state preparation, photon loss, and imperfect detector. Finally, given mean
photon number $\bar N=2.297$ and $\ell=1$, we show an angular displacement
super-resolution effect with a factor of 7.88, and the sensitivity approaching
shot-noise limit is reachable.
