The detection of welding defects type of the specimen made of WELDOX960 steel based on acoustic emission (AE) technology has been investigated. Firstly, three-point bending test on the three kinds of specimens, that is, the specimen with severe slag inclusion, the one with blowhole welding defect and the one with good welded joint was conducted respectively. Then the analysis of AE source characteristics and statistical parameters distribution characteristic were introduced. As the result, for the specimen with severe slag inclusion and the specimen with good welded joint, we find AE characters such as amplitude and energy rate has similar change trend except for the intensity, hit counts and duration time, and the extent of the former one is larger than that of the latter one. However, for the specimen with blowhole defect, along with the whole loading process, the evident AE signal character of crack generation and propagation happen all the time. Also we found the parameter distribution of amplitude, count and duration time of the three kinds of specimens were distinctly different and have its own characters, which indicated that the three kinds of AE source can be distinguished using the AE technology.