The effects of vacuum pressure and gas adsorption on field emission current of alpha-Fe2O3 nanoflakes were studied. It was found that field emission current of alpha-Fe2O3 nanoflakes decreased with increasing pressure. The field emission current decreased when N-2 or O-2 was introduced into chamber, while no obvious change was observed for H-2 gas. An in-situ thermal treatment was carried out to eradicate the effect of absorbed gas. After the in-situ thermal treatment, the field emission current density was largely enhanced from 60 to 500 mu A/cm(2) under applied electrical field of 10 MV/m and the turn on field (Eturn-on) decreased from 7.6 to 5.2 MV/m. The lowered turn-on field was attributed to the decrease of surface work function induced by surface gas desorption and reduction of alpha-Fe2O3 nanoflakes. Moreover, the improvement of field emission performance can be retained in high vacuum condition, which indicates the in-situ thermal treatment is an efficient method to improve field emission properties of alpha-Fe2O3 nanoflakes. (C) 2013 Elsevier B.V. All rights reserved.