In this paper, a new-version microstrip line is proposed, named packaged microstrip line. It is comprised of three dielectric substrates. This novel microstrip line is no longer suffering from the issues of radiation losses, surface waves, or cavity resonances that exist in the standard microstrip line without or with a metallic shielding box. Instead of the packaging way based on the standard air gap waveguide technology, this novel packaged microstrip line has the following merits: greatly reduced weight and size, easy manufacturing, constant gap height and more flexibility in design. We present how to adopt a proper dielectric substrate for each layer of the packaged microstrip line considering both stopband and line losses, and how to design the line width for a given characteristic impedance. One prototype of this proposed novel packaged microstrip lines is fabricated and tested, showing a good agreement with the simulated results.