Abstract: Lignosulfonate/melamine formaldehyde (LS/MF) microsphere foam was prepared by a facilemethod. Both FTIR and theoretical calculations were applied to explore the reaction mechanism of LS and MF, the effects of dosage of LS on properties were investigated, and the morphology of the LS/MF was studied by SEM. The results show that the prepared LS/MF is constructed by hollow spheres with about 3 μm diameter. Compare to MF foam without LS, the obtained LS/MF hollow sphere foams have the secondary structure:the particles about 200 nm adhere to the spheres surface. LS/MF sphere foam prepared with 15wt% LS shows excellent properties. By this condition, the thermal conductivity coefficient of LS/MF is 0.0216 W(mK)^-1, which is 20% lower than MF without LS. This indicates that the prepared LS/MF sphere foam has excellent thermal insulation property. The LS/MF would have wide application prospect due to the simple preparation method and the low cost.