In this study, we have investigated the effects of Ti buffer layer for the fabrication of MgB2 crystalline film on ZnO (0001) substrate. The Ti buffer layers (thickness of 5-50 nm) and MgB2 films were deposited by molecular beam epitaxy apparatus. The MgB2/Ti bilayers were characterized by in-situ RHEED and ex-situ XRD measurements, and the superconducting properties were studied by magnetic measurements using SQUID magnetometer. It is found that Ti layers were grown epitaxially on the substrates and the MgB2 films were c-axis oriented with two types of in-plane rotational domains. The crystallinity reflected on the rocking curve width and the superconducting transition temperature Tc were enhanced with increasing the thickness of Ti buffer layer. The highest Tc in this study was obtained to be 37 K when the Ti buffer layer thickness is 50 nm.