The invention relates to detectors used when ferry glass reinforced plastic boats are manufactured, in particular to a ferry glass reinforced plastic boat lateral thrust leak tightness detector. The ferry glass reinforced plastic boat lateral thrust leak tightness detector is characterized in that a detecting cover is arranged, a pressurization pipe is connected on the detecting cover, and the other end of the pressurization pipe is connected with a pressurization detector. When the ferry glass reinforced plastic boat lateral thrust leak tightness detector is used, one end of a cylindrical flow channel of a traverse body is sealed while the other end of the cylindrical flow channel of the traverse body is hermetically connected with the detecting cover, the pressurization detector is used for pressurizing into the cylindrical flow channel, whether pressure (height of a water column in the pressurization pipe) of the pressurization detector is decreased or not is observed within a period of time after pressurization is stopped, if yes, the result accounts for poor leak tightness between a lateral thruster and a cabin, and maintenance is carried out after leak points are found. Whether leak tightness between the lateral thruster and the cabin is good or not can be detected and maintained when the boats are manufactured, and accordingly the ferry glass reinforced plastic boat lateral thrust leak tightness detector is simple, laborsaving and timesaving to operate. When slight leak exists between the lateral thruster and the cabin, the slight leak can be displayed on the pressurization detector, and large-area water leak accidents caused by the undiscovered slight leak after the boats are put into use are avoided.