Even if one is only interested in continuum data, the multi-frequency imaging is still relevant. The present SMA observations can simultaneously produce 48 spectral windows with 4 GHz in each side band; and in the near future the SMA will add additional two broad bands with a total of 8 GHz per sideband. Thus one needs to handle 100 spectral windows in the imaging process simultaneously. In particular, for combining the two sidebands with a separation of 10 GHz, the total bandwidth coverage would be large and effects of the frequency smearing and a steep emission spectrum across the observing bands become significant. The frequency-dependent effects must be removed in order to make a high sensitivity continuum imaging by combining all the spectral window data. The technique of forming a single continuum image from a variety of frequencies is called ``multi-frequency synthesis'' (MFS). Miriad supports the MFS feature. The MFS process is useful to SMA users in imaging the continuum dust emission from distant galaxies, planets outside the solar system, young stars in the Galactic center/disk and starburst galactic nuclei. An example of making an image from raw SMA data to final image using MFS technique is shown in the sections below. In addition, we also discuss the weighting methods in the imaging process.