The strong-field processes can be controlled by the waveforms coherently synthesized by multi-color laser pulses. By using the “temporal gate” formed by the optimized two-color chirped laser pulse in the frequency domain， the extension of cut-off energy in the high-order harmonic generation and the generation of isolated attosecond pulse are achieved. By considering the macroscopic propagation effects， the contribution of long-trajectory electron in the high-harmonic emission burst is suppressed， leading to the reduction of its duration， thus the isolated attosecond pulse with the duration of about 200 as is generated in the X-rays， which provides with new hints for producing ultrashort attosecond pulses in the experiments.