The invention provides an added mass vibration inverse algorithm for fluid. According to the algorithm, the fluid is not required to be supposed as ideal fluid, so that the personal and flowing properties of the fluid around a structure can be really reflected; the vibration mode information of the actual structure is used as input data of added mass calculation of the fluid, and the environmental states of the structure are divided into two kinds, namely in air and in fluid; through the vibration test in the two states, the model errors between the actual structure and a finite element model can be considered, and the added mass of each unit in the fluid can be acquired in a matrix form; and the calculated added mass of the fluid exists in the matrix form, so that engineering calculation and analysis are facilitated.