Different from the electrical signal, the optical signal has many problems in split method, such as too big insertion loss, the weak split test signal, and the test signal concerned in the split position. It is often not stable or can't meet the demand and fail in the actual optical communication engineering test process. A full optical design method of active splitter is presented to make full use of the optical amplifiers, which can be used to split test signal in optical fiber network. In addition to meeting the basic requirement of the test signal to have no effect on the original signal, it has a small insertion loss, draws out a strong signal, has a low cost and is unconcerned in test optical signal format etc. With the development of the technology of optical amplifiers, this full optical split method will get more attention.