The invention discloses a novel ultrathin battery and a preparation method thereof. The novel ultrathin battery comprises a battery cathode substrate, a battery anode substrate, a cathode metal mesh, an anode metal mesh, a cathode particle material, an anode particle material and a barrier, wherein the cathode tab and the anode tab of the battery are formed by extending from the cathode metal mesh and the anode metal mesh, respectively; the cathode metal mesh and the anode metal mesh are bonded to the battery cathode substrate and the battery anode substrate, respectively; the cathode particle material and the anode particle material cover the battery cathode substrate and the cathode metal mesh, and the battery anode substrate and the anode metal mesh, respectively; the barrier is arranged between the battery cathode substrate and the battery anode substrate, and the barrier is capable of blocking the battery cathode substrate and the battery anode substrate from each other; the battery is covered with a flexible insulating sealing layer. The novel ultrathin battery and the preparation method thereof have the advantages of simplified production process, low battery production cost, large battery capacity, convenience for application and the like.