A method for detecting an abnormality of a fluid filter includes: detecting a flow rate of a fluid in the fluid filter; detecting a pressure difference in the fluid filter; constructing an operating model of the fluid filter in accordance with a geometry of the fluid filter, a physical characteristic of the fluid, a porosity of the fluid filter, an impurity density, the flow rate and the pressure difference; obtaining an initial impurity accumulative quantity through the operating model; estimating a time dependent impurity accumulative status through a Kalman filter in accordance with the initial impurity accumulative quantity and the pressure difference; obtaining an impurity accumulative quantity in an estimated time in accordance with the time dependent impurity accumulative status, and then comparing the impurity accumulative quantity with a pre-determined value to determine if the fluid filter operates normally.