The invention relates to a pretreatment method for detecting the concentric circle of monocrystalline silicon, wherein a sample block with a circular head of monocrystalline silicon is cut; The obtained monocrystalline silicon head sample block is carved with a diamond pen to obtain a sample of more than 1/4 circle; the obtained sample is annealed; the annealed sample is boiled in alkaline solution; And then the boiled sample is soaked in the acid solution; the sample piece with pure water is washed after soaking the acid solution, and the sample piece is dried in the air; The dried samples are tested for minority carrier lifetime. The invention also provides a pre-treatment method for detecting black angle of monocrystalline silicon. The circular sample block of any monocrystalline silicon tail is cut. The obtained monocrystalline silicon head sample block is engraved with a diamond pen to obtain a sample piece with more than 1/3 circle; the obtained sample is eteched in acidic solution; the sample is cleaned after the acid solution is corroded and the acid liquid remains; the residual sample of the cleaning acid solution is annealed; The annealed sample is air-dried naturally andcooked with alkaline solution; The cooked samples are tested for minority carrier lifetime.