The invention discloses a side rollover prevention structure for a fishing boat and a using method of the side rollover prevention structure, and belongs to the technical field of side rollover prevention structures. The side rollover prevention structure expands to increase the drainage volume, then buoyancy is generated to prevent side rollover, then through signals of a pressure sensor, gas supply is continuously increased to the upper limit value, then pressure sensed by the pressure sensor is reduced, information is sent to a PLC, then the PLC controls an air supply and exhaust pump to pump gas in a second gasbag and gas in a first gasbag separately, so that the rollover prevention structure shrinks to reduce the drainage area, and then automatic rollover prevention is finished. Through the limiting effect of a first limiting spring, a second hinging cylinder and a first hinging cylinder of the side rollover prevention structure form a certain included angle, so that the tail of aship nose is limited, and thus side rollover and front-and-back rollover are automatically prevented. When the side rollover prevention structure is not in use, the gasbags are contracted to avoid the situation that the gasbags are in contact with the water surface and hinder running of a ship body, and meanwhile, the protection effect of rollover prevention is achieved when personnel on the boatpay no attention.