The invention belongs to a telemetry system for the density in a cable branch joint sulfur hexafluoride air chamber, which is characterized in that: a data collection and collating unit uses RS-485 bus to be connected with at least an SF6 density monitor; the data collection and collating unit comprises a data collecting and storing processing unit, a power controlling unit, a key and display unit, a short message receiving/sending unit and a computer interface unit respectively connected with a central processing unit CPU; a GSM short message receiving/sending device is connected on the short message receiving/sending unit; an external power is connected on the power controlling unit. The telemetry system for the density in a cable branch joint sulfur hexafluoride air chamber has the advantages that: a solar energy battery is used as the power supply mode; short messages can be used for sending the monitoring situation of the density gauge two times each day; the density history record of one to two months can be provided for making copies on site and the cellphone number sending the short message can be changed; each line in the case is provided with an SF6 inflatable chamber with a total of three; the SF6 density in the three inflatable chambers can be monitored.