Identifying novel 2D semiconductors with promising electronic properties and transport performances for the development of electronic and optoelectronic applications is of utmost importance. Here, we show a detailed study of the electronic properties and ballistic quantum transport performance of a new 2D semiconductor, SbSiTe3, based on density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalism. Promisingly, monolayer SbSiTe3 owns an indirect band gap of 1.61 eV with a light electron effective mass (0.13m0) and an anisotropic hole effective mass (0.49m0 and 1.34m0). The ballistic performance simulations indicate that the 10 nm monolayer SbSiTe3 n- and p-MOSFETs display a steep subthreshold swing of about 80 mV dec-1 and a high on/off ratio (106), which indicate a good gate-controlling capability. As the channel length of SbSiTe3 decreases to 5 nm, its p-MOSFET also effectively suppresses the intra-band tunneling. Therefore, 2D SbSiTe3 is a potential semiconductor for future nanoelectronics.