A selective motion vector prediction method and a motion estimation method and a device thereof applicable to a scalable video coding (SVC) system are disclosed. The selective motion vector prediction method includes the steps of performing an inter prediction to obtain a first motion vector prediction center; performing an inter-layer motion prediction to obtain a second motion vector prediction center; in the case the first and the second motion vector prediction center satisfying a preset condition, using the same reference data to calculate the rate-distortion costs for the inter prediction and the inter-layer motion prediction; and using the rate-distortion costs as a basis to select one of the inter prediction and the inter-layer motion prediction for applying to the SVC system. Thus, the same reference data is shared to enable reduced memory access in the process of coding and accordingly, reduced cost of and power consumption by memory access.