Based on the Jackson and Hunt's analysis,the selection of lamellar spacing in regular eutectics was re- examined at low velocity.The isothermal assumption was released and the effective interface undercooling was determined by the weighted average of the eutectic phases.It is found that the lamellar spacing minimized the effective interface undercooling depends only on the intrinsic characteristics of a given system at a fixed velocity. In addition,the selection of lamellar spacing is related to the relationship between the average interfacial undercoolings of the eutectic phases and the lamellar spacing.The selected lamellar spacing obviously deviated from that predicted by the Jackson and Hunt's analysis if the variation of the average interfacial undercoolings of the solid phases with the lamellar spacing was markedly different at a constant growth rate. Based on the Jackson and Hunt's analysis, the selection of lamellar spacing in regular eutectics was re- examined at low velocity. The isothermal assumption was released and the effective interface under cooling was determined by the weighted average of the eutectic phases. It is found that the In addition, the selection of lamellar spacing is related to the relationship between the average interfacial undercoolings of the eutectic phases and the lamellar spacing. selected lamellar spacing obviously deviated from that predicted by the Jackson and Hunt's analysis if the variation of the average interfacial undercoolings of the solid phases with the lamellar spacing was markedly different different at a constant growth rate.