A wave coupling theory of linear electrooptic effect has been used to study the temperature dependence of electrooptic modulator. The numerical results of temperature dependence have been obtained from this method under different angels between incident light vector and crystal optical axis. The results show that temperature stability of electrooptic modulator can be obtained by angle modulation. An optimal design of electrooptic modulator has also been presented, which has the advantages of a very small zero-field leakage, a relatively small half-wave voltage, a large extinction ratio and good stability of output intensity versus temperature. And the design doesn't need transparent electrodes.