Electron emission from antiferroelectric ($\rm{Pb_{0.99}Nb_{0.02})[(Zr_{0.80}Sn_{0.20})_{0.952}Ti_{0.048}]_{0.98}O_{3}}$ cathode has been investigated. The PZST cathode can maintain a metastable ferroelectric phase by the application of a high enough field, thus implying three possibly pulse-loading configurations for electron emission measurements. The fact that emission charge is larger than the non-compensated charge indicates that the surface plasma contributes to the total emission charge. Furthermore, $_{χi} (i = \rm{A, B, C})$, characterising the contribution of surface plasma to the total emission charge, was defined. It was found that the emission charge increases almost linearly with $_{χi}$. Our results are of great importance for a better understanding of electron emission in antiferroelectric/ferroelectric cathodes.