Phage phi29, a double-stranded DNA virus, assembles its genome into its protein capsid to near-crystalline density by a highly efficient molecular motor. The motor contains the connector, prohead RNA and ATP hydrolytic enzyme protein gp16. Currently, no structure-function information is available regarding the C-terminal domain of gp16. Our research aims to understand its role and interaction with pRNA or DNA. This study provides a method for recombinant gp16 protein synthesis and purification by the E.coli SUMO expression system, and here we report the structural envelope of the C terminal domain of gp16 obtained through small angle X-ray scattering (SAXS) technology. The gp16 C terminal domain gene was recombinantly expressed using the SUMO tag. The gp16 gene was flanked by an N-terminal 6His-SUMO tag and purified by Ni-NTA affinity chromatography. High purity target protein monomer was obtained by size exclusion chromatography. This brings the purity of the target protein to about 95%. Then the concentration of the target protein to 1.3 g/L, and the SAXS data were collected at Shanghai Synchrotron Radiation Facility (SSRF) beamline BL19U. The resulting molecular envelop highly resembles the homologous protein FtsK, and the curves calculated by the CRYSOL software are highly coincident with the experimental curves. Through recombinant expression, purification and structure analysis, we obtained the solution structure of the gp16. Structural information derived from this study laid the foundation for future structural and functional research of gp16 C terminal, ultimately targeting the viral mechanisms for infection.