Cell-free protein expression system is a new method to express target protein in vitro and has been widely applied to the study of protein structure, protein function and other related fields. Preparation of cell extract is one of the key factors that affect the efficiency of the cell-free system. To improve the efficiency and economical feasibility of cell-free protein synthesis, we discussed the parameters during the preparation of the cell extract. These parameters include centrifugation speed, pre-incubation, and dialysis. We used the green fluorescent protein as the reporter protein, and obtained a simple procedure for the preparation of Escherichia coli cell extract. A simple centrifugation step (12 000 x g, 10 min) followed by a brief incubation was sufficient for the preparation of an active cell extract to support protein expression with higher productivity (209 microg/mL). Compared to the traditional E. coli S30 procedure, the processing time was reduced by 62%, and the productivity was increased by 2.6 times. The new procedure will make the advantage of cell-free technology more obvious, and promote its wider application.