This paper first elaborates the domestic and foreign study and applying current situation in terms of the concrete testing field regarding to acoustic emission technology, especially the study progress in the large dam concrete field. By improving the current test device and updating and reforming the measuring equipment, the task team introduces the acoustic emission testing system into the concrete double-K fracture parameter test. The new device can not only accurately control the loading velocity in the test, but also correctly judge the time and property of cracking, instability and damage of specimen. This paper establishes the acoustic emission criterion for concrete fracture according to the recognition features of acoustic emission of concrete in fracture critical state. The test result presents that the cracking time of specimen can be correctly judged by using feature parameters of acoustic emission, which properly matches the cracking time measured by the traditional strain method, and this judging is more direct and convenient for on-site operation, providing theoretical and technical support for application in the concrete fracture parameter test by acoustic emission technology.