Poly-gamma-glutamic acid (gamma-PGA) is a novel biodegradable polyamide material. Microbial fermentation is the only way to produce gamma-PGA, but the molecular weight of gamma-PGA varied depending on different strains and culture conditions used. The molecular weight of gamma-PGA is a main factor affecting the utilization of gamma-PGA. It is urgent to find an efficient way to prepare gamma-PGA with specific molecular weight, especially low molecular weight. Bacillus subtilis ECUST is a glutamate-dependent strain that produces gamma-PGA. In this study, a recombinant B. subtilis harboring the gamma-PGA synthase gene cluster pgsBCAE of our preciously identified gamma-PGA-producing B. subtilis ECUST was constructed. Assay of gamma-PGA contents and properties showed that recombinant B. subtilis 1A751-pBNS2-pgsBCAE obtained the ability to synthesize gamma-PGA with low molecular weight (about 10 kDa). The excessive addition of glutamate inhibited the gamma-PGA synthesis, while the addition of Zn2+ could promote the synthesis of gamma-PGA by increasing the transcription of pgsB but had no effect on the molecular weight of synthesized gamma-PGA. Under optimized conditions, gamma-PGA produced by recombinant B. subtilis 1A751-pBNS2-pgsBCAE increased from initial 0.54 g/L to 3.9 g/L, and the glutamate conversion rate reached 78%. Recombinant B. subtilis 1A751-pBNS2-pgsBCAE has the potential for efficient preparation of low molecular weight gamma-PGA.