A writer for a tire pressure sensor is disclosed, which is adapted to hold the tire pressure sensor to write a program to the tire pressure sensor. The tire pressure sensor has a first connection port. The writer includes a housing, a positioning member, and an ejection device. A surface of the housing forms a receiving recess, and a second connection port is provided in the receiving recess. When the tire pressure sensor is received in the receiving recess, the first connection port thereof is connected to the second connection port. The positioning member connected to the housing has a block section abutting against the tire pressure sensor to keep the first connection port being connected to the second connection port. The ejection device is adapted to exert a pushing force on the tire pressure sensor to eject it for separating the second connection port from the first connection port.