The traditional detection method of abrupt change may pay more attention on the "point of abrupt change" and neglect the process of its onset, development and extinction. This paper has proposed a new detection method to obtain the abrupt change process (ACP); it can extract suitable parameters from real time series by using a piecewise function which is based on a logistic model that reflects the ACP. With the help of parameters' physical meaning, we researched and analyzed the whole ACP, deepened the understanding and awareness of ACP, to lay the scientific foundation for further study on the formation mechanism, affecting factors and trends of the abrupt change. Besides, by detecting the PDO time series' ACP, we also find that the time series began to change in 1940/1942, 1977, 1987, and the duration of abrupt change is locked in some fixed values; furthesmore, the phase graph of the system showed that a normal system world have 3 basic states.