A strong piezoresistive effect of GaAs micro-structure which is based on high electron mobility transistor (HEMT) is reported in this paper. The GaAs HEMT is embedded in the root of the cantilever as the sensitive element in order to detect the deformation. The strain is simulated with the ANSYS software, and the maximum gauge factor is about 26,350, which is nearly a hundred times larger than that of piezoresistive silicon. The high gauge factor is not only due to the option of voltage bias, but also the combination of the piezoresistive and piezoelectric effect. The obtained results demonstrate that GaAs micro-structure based on HEMT can be suitable for high sensitive stress/pressure sensors. (C) 2011 Published by Elsevier Ltd.