The test beam running on the linear electron accelerator (LINAC) of BEPC as parasitical mode is one and only beam line of particles with middle energy in China. It consists of E1 line E2 line and E3 line. Among them, E3 line is the secondary particle beam which includes e^¡À, ¦Ð^¡À and proton. The momentum of the particles can be adjusted between 300MeV/c and 1.1GeV/c by D2 magnet according to different requirement.