Abstract: OBJECTIVE To combine the method of W/O/W with micro-injection and study the application of micro- injection on preparing sustained release biodegradable octreotide microspheres. METHODS It was studied by using a single factor analysis method on spray frequency, agitation speed and driving voltage as the factors. RESULTS In the constant prescription conditions, the driving voltage was proportional to the particle size, the spray frequency and mixer speed were inverse ratio to the particle size. When the driving voltage was 60-100 V, spray frequency was 3 000-7 000 Hz and agitation speed was 150-450 r·min^-1, the particle size distribution was in more ideal state. CONCLUSION The microsphere prepared by micro-injection are in rounded appearance and well formed. This method significantly improves uniformity and appearance compared with microsphere prepared simply by W/O/W, and there is a certain increase in encapsulation efficiency(>30%).