We hope to verify the conservation of orbital angular momentum (OAM) of light under the spontaneous parametric down-conversion (SPDC) process. We use laser(with 355nm-wavelength) to pump a β − BaB2O4 (BBO) crystal. Because of the nonlinear property of the BBO crystal, the degenerate SPDC could happen in the crystal. Therefore, one 355nm photon would converted to two 710nm photons. We make use of the birefringence property of the BBO crystal to achieve beamlike Type II phase-matching. Under this phase-matching, it is efficient to collect the down-converted 710nm light. We plan to make the pump light carry the OAM with l = 0 or l = 1 by means of the hologram. On the other way, we use a new-reported method to measure the OAM of the down-converted 710nm light. And, making use of the coincidence-counting tool, we could verify the conservation of OAM of light. Under the SPDC process, the down-converted 710nm photon pairs are in the entangled state. Therefore, this experiment is related to the OAM of light and the entangled state which the quantum theory predicts. These two subjects are worthy of studying.