The invention pertains to the field of stationery, and relates to a pen holding posture alarm system. The pen holding posture alarm system comprises a sleeve body portion, a holding portion and an alarm portion. The sleeve body portion is provided with an adjustment device which is compatible with an ordinary pencil refill and a gel pen refill. The alarm portion is disposed at the upper end of the sleeve body portion and is formed by connecting a silver oxide cell, a single toggle switch and an active buzzer in series. The holding portion is disposed at the lower end of the sleeve body portion and is formed by connecting three normally closed pushbuttons in parallel, and the three normally closed pushbuttons are arranged around the lower portion of the cylindrical pen sleeve successively at a certain distance. The holding portion and the alarm portion are connected in series through a wire. The system can be installed on a cylindrical pen sleeve which is made of a high-polymer material. The system has the functions of alarming a user about a pen holding posture error timely and changing the wrong pen holding method timely. The system has advantages of conciseness, small size, light weight and stable center of gravity, the holding and writing of users are not affected, and the system can help users to master the correct pen holding posture and reduce the visual fatigue.