Fast steering mirrors (FSMs) are typically applied for beam stabilization for precision pointing and tracking systems (PPTSs) owing to their high-bandwidth, high-resolution, and high accu-racy. In addition to the advantages, the presence of the residual momentum which caused by FSMs' operation usually has noticeable effects on the stabilization of the line of sight (LOS) for PPTSs. Hence, it is necessary and momentous to estimate the effects of these disturbances to give insight into the FSM specification and the PPTS structural performance. However, the characteristic of multidisciplinary coupling makes it a challenge to measure the LOS jitter caused by FSMs. We approach this problem by establishing an integrated model for estimating the LOS jitter. A dynamic model of an FSM is firstly built to value the unbalanced momentum generated from its motion. Then a finite element model for the structure of the tracking system is established to predict the dynamic response excited by the disturbances from the FSM. In addition, with a linear optical model, the system optical performance under the FSM's disturbances is determined. Finally, a test is conducted to verify the validity of the model and the analysis. This paper focuses on estimating the disturbances effects of the FSM on the LOS jitter for a PPTS, and providing potential approaches for reducing these effects.