To identify the generated source of coupling errors, design method of the flexible eccentric mechanism is discussed in the paper. Firstly, the composition and working principle of the mechanism is given. Then, the mechanism model is established based on the compliance matrix method(CMM). Compliance of the bridge-type displacement amplification mechanism, the guiding mechanism and the connecting mechanism is derived. Finally, compliance of the whole body is got. The results show that the output compliance error is 8.126% obtained by the CMM and FEA method. The first natural frequency of the mechanism is 73.78 Hz. The stroke of the mechanism is 66.466μm when the driving force is no more than 40N. The maximum stress on lens and mechanism is 0.0711MPa and 235.22 MPa, respectively. The coupling error ratios between Y/Z/RX/RY/RZ and X stroke are 0.0543%, 0.0082%, 1.218×10－8rad/μm, 1.870×10－7rad/μm and 6.073×10－7rad/μm. PV and RMS of the lens surface figure after adjusting are better than 24nm and 5nm, respectively. It is mainly astigmatism. The mechanism is almost completely decoupled by reasonable flexibility design, which reveals that unreasonable compliance is the root of the generated coupling errors in adjusting.