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abstract: 'We present results from a test for the Gaussianity of the whole sky sub-degree scale CMB temperature anisotropy measured by the Wilkinson Microwave Anisotropy Probe (WMAP). We calculate the genus from the foreground-subtracted and Kp0-masked WMAP maps and measure the genus shift parameters defined at negative and positive threshold levels ($\Delta\nu_{-}$ and $\Delta\nu_{+}$) and the asymmetry parameter ($\Delta g$) to quantify the deviation from the Gaussian relation. At WMAP Q, V, and W bands, the genus and genus-related statistics imply that the observed CMB sky is consistent with Gaussian random phase field. However, from the genus measurement on the Galactic northern and southern hemispheres, we have found two non-Gaussian signatures at the W band resolution ($0\fdg35$ scale), i.e., the large difference of genus amplitudes between the north and the south and the positive genus asymmetry in the south, which are statistically significant at $2.6\sigma$ and $2.4\sigma$ levels, respectively. The large genus amplitude difference also appears in the WMAP Q and V band maps, deviating the Gaussian prediction with a significance level of about $2\sigma$. The probability that the genus curves show such a large genus amplitude difference exceeding the observed values at all Q, V, and W bands 