Based on the present geometry delay models of GNSS-R (global navigation satellite systems reflectometry) spaceborne altimetry, dynamic error and parallel signal error are studied. Apart from analyzing the reasons causing these two errors, this paper gives the analytical expressions of both errors. In order to obtain the magnitudes of dynamic error and parallel signal error, this paper first utilizes a segment of actual experimental data from the satellites of UK-DMC (united kingdom disaster monitor constellation) to test the magnitudes of dynamic error and parallel error, getting both errors of this set of data. Furthermore, regarding CHAMP (challenging mini-satellite payload) and COSMIC (constellation observing system for meteorology, ionosphere and climate) satellites as the platforms of receivers, a host of simulated data are used to detect the magnitudes of both errors. The conclusion that these two errors can be as great as the meter level, which cannot be ignored in altimetry, is reached after considering the results of two kinds of experiments. Finally, a solution of using the precise orbits information of transmitter and receiver to adjust dynamic error and parallel signal error is proposed.