A lamp source module includes a holder having an air inlet and an air outlet, a gas discharge lamp having a lamp reflector assembled onto the holder and a burner disposed in the lamp reflector, a light cover assembled on the holder and surrounding the lamp reflector, a blower duct communicating with the air inlet and extending along the exterior of the lamp reflector to the bottom of the lamp reflector, and an airflow generator communicating with the blower duct and capable of providing a cooling airflow. The air inlet is capable of causing the cooling airflow to enter the blower duct. The blower duct is capable of directing the cooling airflow to the bottom of the lamp reflector to make the cooling airflow pass through a sandwiched space surrounded by the lamp reflector and the light cover and then discharge from the air outlet.