The porous silicon (PS) was prepared by means of irradiation with He-Ne laser beam for the first time. Polished n-type(100) silicon wafers with resistivity 2-3Ω·cm were used as substrate. The silicon wafers were immersed in HF-H

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O solution without current and irradiated with He-Ne laser beam. The position of PS formation is freely selected and the size of PS can be controlled by this technique.The surface morphology differs from that of anodized PS. It presents a distinct interference fringes. PL spectrum shape is similar to that of anodized PS. The samples excited by UV light or 488nm line from Ar ion laser at room temperature show intence red or orarge colour luminescence. It is found that the peak shifts to shorter wavelength and the PL intensity is obviously increased as the irradiating time is increased. Our experimental results show that this technique is not fit for p-type silicon wafers.