With the adsorption of analyte on the resonator mass sensor, the system eigenfrequencies will shift due to the changes of inertial mass and structural rigidity. How to model those changes and formulate the eigenfrequency computation is very important to the mass sensor application, which results in different accuracies and requires different amounts of computation. Different methods on the eigenfrequency computation of a beam and a plate carrying arbitrary number of concentrated mass/spring are presented and compared. The advantages and disadvantages of these methods are analyzed and discussed. A new method called finite mode transform method (FMTM) is shown to have good convergence and require much less computation for a beam carrying concentrated mass/spring. Because the previous finite sine transform method (FSTM) has only been applied to compute the eigenfrequency of the plate with four edges simply supported carrying a single concentrated mass, here a generalized FSTM is also presented for the case of the same plate carrying arbitrary number of concentrated mass and spring. When the total number of concentrated mass and spring is small, FMTM and FSTM are demonstrated to be very efficient.