A weak signal detection device and method based on wavelets and a radial basis function (RBF) neural network belong to the technical field of signal detection. The device comprises a fourth-order Butterworth low pass filter, an A/D converter, an ARM microprocessor, a synchronous dynamic random access memory (SDRAM), a Nor Flash memory and a N and Flash memory. The device is beneficial to inhibiting noises and restoring, enhancing and extracting useful signals. The method can realize detection of a few oil leakage accidents which can not be detected by the conventional leakage detection devices and detect fluctuation less than 3%.