The invention relates to a liquid level seal connector and an underwater connection signal transmission and air guide method thereof. The connector comprises a cable. One end of the cable is sleeved by a casing cap. The front end of the casing cap can be sleeved in a sensor casing body of a transmitter sensing part. A first sealing device is arranged at the joint of the casing cap and the sensor casing body. A second sealing device which is used for sealing the cable and the casing cap is arranged on the tail end of the casing cap. A plug of a connector is arranged in the casing cap. The plug is connected with the cable. The socket of the inserter is arranged in the sensor casing body and is connected with a transmitter signal line, so as to form an integral connector structure. According to the invention, the casing cap is sleeved in the sensor casing body; the transmitter sensing part, the cable and a power supply can be flexibly separated, which is convenient for replacement and maintenance; through first and second sealing devices, the casing cap and the sensor casing body are sealed to form a cavity; the cable, the plug and the socket are arranged in the cavity and are effectively isolated from an external medium; and the liquid level seal connector has the advantages of good sealing effect, high protection degree and great reliability.