The invention relates to a pen incapable of being opened by a child. The pen comprises a pen holder, a pen case and a pen refill, the pen refill is arranged in the pen holder, a first press rod capable of pressing the pen refill out of the pen holder is arranged in the pen case, a plurality of fixing rods are fixedly arranged outside the pen case, bumps are arranged on sides of the fixing rods, the outer side wall of the pen holder is rotatably connected with a plurality of arc-shaped fixing plates, through holes are formed in all the arc-shaped fixing plates, the width of each through hole is matched with that of each fixing rod, sliding grooves matched with the bumps are horizontally formed in the inner walls of the through holes, a first baffle plate is fixedly arranged on the outer side wall of the pen refill, a plurality of annularly distributed holes are formed in the pen holder, the press rod penetrates the holes and extends into the pen holder, and a second baffle plate is fixedly arranged at one end of the press rod positioned in the pen holder and is connected with the inner side wall of the pen holder through a first elastic component. The child can be prevented from opening a pen cap or pressing out the pen refill, and safety is high.