The invention discloses a device and a method for detecting and positioning leakage of a gas transmission pipeline based on conventional data and sound wave signals. The detecting device comprises a sensor group, a field data acquisition processor, a global positioning system (GPS) receiver, a communication network, a central data gathering processor and a monitoring host. The detecting method comprises the following steps of: respectively acquiring sound wave data and traffic, pressure and temperature conventional data of the upstream and the downstream of the pipeline, filtering background noise from the sound wave data by using wavelet transform, respectively identifying a time domain, a frequency domain and time and frequency domain characteristics of the sound wave signals by combining the conventional data to remove external interference and realize leakage signal characteristic extraction, performing leakage positioning by adopting an improved positioning method based on a related analysis method and a GPS synchronous time method, and giving a theoretical installation distance of sound wave sensors according to a propagation model of the sound wave signals. An interface can be established between the conventional data and a field supervisory control and data acquisition (SCADA) system, and only the sound wave sensors are arranged on the upstream and the downstream of the pipeline, so that the invention has the advantages of low investment, high equipment sensitivity and strong adaptability.