Abstract: In this paper, "Similar Cycle" method is introduced and smoothed monthly mean F_10.7 flux of cycle 23 is predicted in two approaches and then the prediction is tested. In the first one smoothed monthly mean sunspot numbers of cycle 23 is obtained by "Similar Cycle" method and then smoothed monthly mean F_10.7 flux is predicted according to statistical relationship between sunspot numbers and F_10.7 flux. In the second approach the "Similar Cycle" method is directly applied to predict smoothed monthly mean F_10.7 flux of cycle 23 by using historical data of past solar cycles. From the prediction, three results are obtained: 1) Both of these two prediction results are close to observations, both having double. 2) The second prediction is closer to the observation than the first one, which shows that F_10.7 flux has similar varing trend with sunspot numbers, but still has its own local varing characters. This can be proved by the second peak of observed F_10.7 flux in cycle 23. 3) Using "Similar Cycle" method, the "Shape" of F_10.7 flux in a solar cycle can be described well, which is difficult to get by other methods.