[Background] Study on the gravel size of gobi surface provides a better understanding about gobi characteristics, and analyzing the reasons of natural disasters in association with gobi. It can also be used to know better about sand migration, desert spread and provide the guidance of sand control engineering. [Methods] In alluvial fanof Gaxun Gobi, the grain size composition,average grain size, sorting coefficient, skewness and kurtosis from 21 gravel samples were analyzed by means of field investigation and granulometry. [Results] The results showed: 1) The major grain size of surface gravels was occupied by mediumsize ones (66.35% -95.04%) due to the effect of flooding, gravity and wind erosion. The size on the top of altitude was dominant by stone (85.54%), average size was - 9.09(545.2 mm). The content of mediumsize gravels decreased while the coarse size gravels increased with the altitude increasing. 2) The average range of size variation was - 9.09(545.2 mm) - -6.15(153.9 mm); the gravels were well sorted (0.28 -0.53) except for sample 12. The grain skewness of surface gravels was dominant by negative, accounting for 80.95%, and the surface gravel size was mainly fine and medium. The kurtosis was flat and very flat (80.95%), followed by medium (23.81%), while sharp or very sharp accounted for 19.05%, which showed the granularity characteristics were evenly distributed. 3) There was no significant correlation between sorting coefficient and average grain size, while there was positive correlation between skewness and average grain size. [Conclusions] The research result can provide useful instructions for lithology of the provenance and gobi development condition.