In this paper, we simulate quantum size effect related to the electronic properties of silicon based single electron transistor (SET). We assume that each electron interacts each other in term of Coulomb blockade effect. These electrical characteristics involve conductance and I-V characteristic of SET structure. Here, quantum size effect corresponds to the size of quantum dot (QD) in which we selected QD size in the range of 1-6 nm. The simulation results show a significant oscillation of conductance and source-drain current (I sd) when the gate voltage is varied. Obviously, by increasing the size of QD the oscillation of conductance and Isd increases as well. In contrast, the oscillations range reduced when the size of QD is increased for both, conductance and Isd characteristics. This result confirms that the bigger QD contains the higher number of electron and the less spacing energy between individual electrons in the QD. Besides conductance, the simulation results of the I-V characteristics demonstrated the staircase profile. This result indicates that one by one electron transfer occurs at certain voltages. Additionally, the staircase profile changes with increasing the number of step when the size of QD is increased as the indication of the increasing of containing electron number in the QD.