The smart noise interference of intermittent sampling noise modulation and forwarding is always difficulty in radar interference countermeasures based on the analysis of the interrupted-sampling repeater jamming (ISRJ) principle. ISRJ is discontinuous in time domain.  An anti ISRJ method based on the stepped linear ferquency modulation (LFM) waveform is proposed. This method utilizes the sub-pulses’ orthogonality to cover each other. The frequency stepping between sub-pulses makes it impossible to interfere with the adjacent sub-pulses after the interference sampling segment is modulated, so that the signal segment without sampling of the jammer can be effectively extracted, which has obvious advantages in the counter against repeated forwarding interference with high duty ratio. Under the simulation condition, when interference sampling and transmitting waveform are out of step, the output signal to jamming plus noise ratio of the narrow sub-pulse is about 3.1 dB higher than that of the wide subpulse.