A pump-probe setup is used for experimental study and it is found that an obvious dark-center diffraction appears at the transmission direction of probe beam when the chromium films is excited by the femtosecond pulse laser and the continuous-wave (CW) laser and when the laser power reaches a certain level. While the dark diffraction phenomenon disappears without the pump beam. This reversible diffraction phenomenon is explained by using the binary phase plate theory. It is also found that the phase change induced by the femtosecond pulse laser is larger than that by the CW laser. The experimental and theoretical results can contribute to understand the mechanism of the interaction between the chromium films and the femtosecond pulse laser and the CW laser.