AcerDET: a particle level fast simulation and recosntruction package for phenomenological studies on high pT physics at LHC. This paper documents package for the particle level fast simulation. The package is designed to complete the AcerMC generator framework with the easy-to-use simulation and reconstruction algorithms. The package provides, starting from list of particles in the event, the list of reconstructed jets, isolated electrons, muons and photons and reconstructed missing transverse energy. The AcerDET represents a simplified version of the package called ATLFAST, used since several years within ATLAS Collaboration. In the AcerDET version some functionalities of the former one have been removed, only the most crucial detector effects are implemented and the parametrisations are largely simplified. Therefore it is not representing in details neither ATLAS nor CMS detectors. Nevertheless, we believe that the package can be well adequate for some feasibility studies of the high pT physics at LHC and in future, after some adjustments, of other detectors as well.