Provided is a crystalline form E of ertapenem sodium. Further provided is a method for preparing a crystalline form E of ertapenem sodium characterized by using an aqueous ertapenem sodium solution at a low concentration as a raw material. The crystalline form E can be easily filtered and dried the properties in the drying process are stable and the purity of the crystal is high and can be up to 98.5% or higher.

Provided is a crystalline form E of ertapenem sodium. Further provided is a method for preparing a crystalline form E of ertapenem sodium characterized by using an aqueous ertapenem sodium solution at a low concentration as a raw material. The crystalline form E can be easily filtered and dried the properties in the drying process are stable and the purity of the crystal is high and can be up to 98.5% or higher.

Intermediates of Ertapenem of formula 2a wherein Np represents (I) or (II) and P1 and P2 represent carboxyl protecting groups and their preparation methods. Compound 2a prepared by the present methods in solid form is amorphous. The present invention also relates to a composition comprising at least 95% of the intermediate of Ertapenem of formula 2a.