The mannose-specific GNA (Galanthus nivalis agglutinin, snowdrop lectin) are the resistant proteins with many bioactivities. Snowdrop lectin is different with plant organs and development periods in lectin species, content, and bioactivities. It is an effective and cheap way to obtain much active GNA through overexpression of GNA gene in Escherichia coli. Constructs encoding mature GNA fused with an N-terminal pelB signal sequence protein (PelB) were expressed in E. coli with high efficiency. Recombinant protein productivity was higher than values published before. The insecticidal activity of purified recombinant proteins was assayed on feeding sugarcane wooly aphid (Ceratovacuna lanigera Zehntner), as well as spraying on sugarcane plants infected by aphids. The insecticidal activity was found to be comparable to native GNA. Oral delivery has obvious positive implications for crop protection against insect pests since peptides can be present in, or sprayed on, plant tissues susceptible to damage. A highly efficient expression of functional recombinant GNA would decrease the cost of GNA and promote its wide use, especially to give crop protection in the field.