  The energy recovery linac test facility (ERL-TF), a compact ERL-FEL (free
electron laser) two-purpose machine, was proposed at the Institute of High
Energy Physics, Beijing. As one important component of the ERL-TF, the
photo-injector started with a photocathode direct-current gun was designed and
preliminarily optimized. In this paper an evolutionary genetic method,
non-dominated sorting genetic algorithm II, is applied to optimize the injector
beam dynamics, especially in the high-charge operation mode. Study shows that
using an incident laser with rms transverse size of 1~1.2 mm, the normalized
emittance of the electron beam can be kept below 1 mm.mrad at the end of the
injector. This work, together with the previous optimization for the low-charge
operation mode by using the iterative scan method, provides guidance and
confidence for future constructing and commissioning of the ERL-TF injector.
