A rail train sidewall, comprising a wall body and a glass window mounted to the wall body, the wall body comprising an inner wall plate and an outer wall plate connected to each other, wherein: the wall body is a double-layered sandwich structure, a partition chamber configured to convey air-conditioning airflow is provided between the inner wall plate and the outer wall plate, an upper end of the partition chamber is located at an upper part of the wall body and is provided with an air inlet configured to communicate with an air supply passage at a top of a carriage, and a lower end of the partition chamber is located at a lower part of the wall body and is provided with an air outlet configured to communicate with an inside of the carriage, characterised in that at each of positions at two sides of a portion where the inner wall plate is connected to the lower end of the glass window, an auxiliary air port configured to blow the air-conditioning airflow towards a glass is provided, and the auxiliary air ports face upwards and are in communication with the partition chamber, wherein a diamond-shaped diverter is arranged in the partition chamber, two ends of the diamond-shaped diverter in a longitudinal direction of the diamond-shaped diverter are respectively located below the two auxiliary air ports, the diamond-shaped diverter is located below the glass window and has upper air guiding slopes and lower air guiding slopes, the upper air guiding slopes are left-right symmetric and configured to divert the air-conditioning airflow to the auxiliary air ports, and the lower air guiding slopes are left-right symmetric and configured to divert the air-conditioning airflow to the air outlet. the wall body is a double-layered sandwich structure, a partition chamber configured to convey air-conditioning airflow is provided between the inner wall plate and the outer wall plate, an upper end of the partition chamber is located at an upper part of the wall body and is provided with an air inlet configured to communicate with an air supply passage at a top of a carriage, and a lower end of the partition chamber is located at a lower part of the wall body and is provided with an air outlet configured to communicate with an inside of the carriage, characterised in that at each of positions at two sides of a portion where the inner wall plate is connected to the lower end of the glass window, an auxiliary air port configured to blow the air-conditioning airflow towards a glass is provided, and the auxiliary air ports face upwards and are in communication with the partition chamber, wherein a diamond-shaped diverter is arranged in the partition chamber, two ends of the diamond-shaped diverter in a longitudinal direction of the diamond-shaped diverter are respectively located below the two auxiliary air ports, the diamond-shaped diverter is located below the glass window and has upper air guiding slopes and lower air guiding slopes, the upper air guiding slopes are left-right symmetric and configured to divert the air-conditioning airflow to the auxiliary air ports, and the lower air guiding slopes are left-right symmetric and configured to divert the air-conditioning airflow to the air outlet.