A new tunable chromatic dispersion (CD) compensating method is presented based on the nonlinear effect of semiconductor optical amplifier (SOA). The compensation effect and range of dynamical chromatic dispersion is simulated and analyzed using the XPM of SOA on the 10 Gbit/s and 40 Gbit/s RZ code systems. The analyzing results indicate that its compensating range can reach 400 ps/nm in the 10 Gbit/s transmitting system and 40 ps/nm in the 40 Gbit/s transmitting system. The experiment of dynamical chromatic dispersion compensation is conducted in the 10 Gbit/s transmitting system on the basis of the analytical results. The experimental result shows that the dispersion compensating rage of -40～60 ps/nm is realized.