The invention relates to a safety pen prevented from being opened by a child. The safety pen comprises a penholder, a pen cap, a drive device and a refill. The refill is arranged in the penholder, a protrusive ring is arranged on the refill, an elastic assembly is arranged at the front end of the refill in a sleeved mode, and the drive device comprises a connecting rod, a clamping head and a positioning device. The connecting rod is fixedly connected with the clamping head which is connected with the refill, protrusive strips are arranged on the side edge of the clamping head, grooves are formed in the lower end of the pen cap, the upper ends of the protrusive strips are matched with the grooves, the positioning device is fixed in the penholder, and the positioning device comprises sliding strips. The ends of the sliding strips are inclined planes, and stopping strips are arranged between the sliding strips at intervals. The refill comprises an upper portion of the refill and a lower portion of the refill. The protrusive ring is arranged on the lower portion of the refill, a first through hole is formed in the penholder, a pull rod is arranged to be fixedly connected with the upper portion of the refill, a first groove is formed in the lower portion of the refill, a flexible fixing part is arranged, pressure rods are arranged on the flexible fixing part, and the pressure rods penetrate through the first through hole to extend to the outside of the penholder. The child can be prevented from opening the pen cap or the pressing the refill out, and therefore safety is high.