A 1×4 multimode interference (MMI) optical power splitter is designed by means of guided-model propagation analysis. Considering the possible factors which would influence the properties of the device in the procedure of designing and fabricating, the influence of the parameters was analyzed, such as the width, the length and the index of waveguide, on the performance of the device. Then the MMI optical power splitter is fabricated and measured. The measuring results show that the fuction of the fabricated device can be realized. In accordance with the problems occured during the experiment and measurement, opinions and methods are presented to improve the performance of the device.