The magnetohydrodynamic (MHD) disk wind is one of the mechanisms to transport the angular momentum of disk materials in protoplanetary disks. Although high-velocity winds/outflows/jets are easily observed at the optical regime, low-velocity winds are rarely detected. In this study, we investigate how to detect the MHD winds with CO and CN emission lines in mm-wavelengths by ALMA. We briefly introduce our ALMA observation of the RU Lup disk and describe a pipeline to examine the MHD wind signature hidden in the line spectra by comparing our data with a simple parameterized disk wind model.