In view of the problem that laser fuze is easily interfered by fog and smoke, a new laser fuze anti-interference method based on pulsed width modulation technique was proposed. The fog echo signal power of different pulse width was computed, and the variation of echo signal power under the influence of transmitted pulse duration was given. The echo signal power ratio in different fog and aerosols environment was analyzed by using different pulse width to detect. The experiment results show that by using different pulse width to detect, the ratio of backscattering power is usually more than 3. Therefore, this method can be used to improve anti-interference ability of laser fuze.