Influence of MgO and K2O on the nucleation behavior of Al2O3-poor LAS (Li2O-Al2O3-SiO2) base glasses was investigated by thermal analysis and, the effect on microstructure and surface topography of glass-ceramics was also examined by SEM, AFM and TEM. According to results of thermal analysis, the exothermic peak temperature of the glass showed a decrease with increase of nucleation temperature to nucleation time of 6 h. But some glasses nucleated for 9 h showed nucleation rate-like curve with maximum point. The dependence of reciprocal value of the exothermic peak temperature on the nucleation temperature indicated that an introduction of MgO might accelerate the nucleation of the base glass and thus result in rough surface topography of glass-ceramics. On the other hand, in the case of glass-ceramics containing K2O the main crystalline phase was lithium metasilicate and they showed fine microstructure resulting in smooth surface topography. TEM micrographs of as-quenched and nucleated glasses showed no trace of phase separation affecting nucleation or final microstructure.