Row crop can be classified between homogeneous and heterogeneous canopy due to its own special geometric characteristics. The footprint uncertainty problem of this kind of canopy should not be neglected in the field directional measurement. This study introduces an equivalent footprint of sensor's field of view into the original Kimes model and develops a footprint uncertainty analysis model for multiangular in situ measurements of row crops through disassembling the equivalent footprint. Both the influences of footprint uncertainty on the four component proportions (i.e. the proportion of sunlit and shaded vegetation, and sunlit and shaded soil) and canopy BRF have been analyzed: ①BRF error is nearly independent of the spectral contrast between vegetation and soil. ②The relationship between BRF error and view zenith angle is very complicated with the forward observation worse than the backward.③Both the errors of four component proportions and canopy BRF keep relatively small and steady after the nadir footprint reaches more than 1 row period. When the nadir footprint is 2 row periods, both the errors arrive at local minimum. Here the ‘local’ means the error might be smaller when the nadir footprint contains more than 2.5 row periods which is beyond the discussion of this study. ④The relative mean error range of BRF is 38.7%～67.8% when the nadir footprint contains only half row period. This range changes into 6%～12% and 0.6%～3.9% when the nadir footprint contains 1 and 2 row periods respectively.⑤Errors are somewhat higher when the nadir footprint contains non-integral period which is between 1 and 2 row periods than it contains just 1 period. So considering the one period situation before the nadir footprint reached 2 periods in the field experiment is the suggestion. This study also compares the proposed and the original Kimes model to the field directional observation of corn canopy in the Heihe River basin based on a multivariate constrained nonlinear optimization technique. The results are consistent with the simulation conclusions above, which include that the footprint uncertainty problem can be ignored when the nadir footprint reached more than 2 row periods and it′s necessary to consider the problem if the nadir footprint contains less than 1 period.