Novel organophosphorus extractants, which have two functional moieties in the molecular structure, were developed for the recycle system of transuranium elements using liquid-liquid extraction. The synthesized extractants showed extremely high extractability to lanthanides elements compared to those of commercially available extractants. The results of extraction equilibrium suggested that the structural effect of extractants is one of the key factors to enhance the selectivity and extractability in lanthanides extractions. Furthermore, molecular modeling was carried out to evaluate the extraction properties for extraction of lanthanides by the synthesized extractants. Molecular modeling was shown to be very useful for designing new extractants. The new concept to connect some functional moieties with a spacer is very useful and is a promising method to develop novel extractants for treatment of nuclear fuel.