Abstract: Effects of plasma density and current ramp up rate on runaway electrons is investigated in current ramp-up phase. It is found that higher density and lower current ramp-up rate can reduce generation of runaway electrons in current ramp-up phase, even in current flat-top phase. Low plasma density will result in hard runaway electrons emission. Lower hybrid wave (LHW) can drive plasma current in order to reduce loop voltage and save volt-second product of Tokamak in current ramp-up phase. Runaway electrons can also be restrained because of reduced loop voltage.