The invention provides a heavy metal wastewater adsorbing material and a preparation method thereof. The preparation method of the heavy metal wastewater adsorbing material includes: adding HCL solution into activated clay and soaking the activated clay for 10-60 minutes to obtain acidized activated clay; mixing the acidized activated clay with water, and stirring for 20-50 minutes at the water bath temperature of 45-70 DEG C to obtain treated activated clay; mixing lignocellulose with NaOH solution, and stirring for 20-50 minutes at the water bath temperature of 40-75 DEG C to obtain treated lignocellulose; mixing the treated lignocellulose with the treated activated clay according to the weight ratio of 1:1-6:1, heating to reach the temperature of 25-75 DEG C, stirring for 2-7 hours, and performing washing, suction filtration, drying, grinding and sieving to obtain the heavy metal wastewater adsorbing material. The heavy metal wastewater adsorbing material prepared by the preparation method is a heavy metal ion industrial wastewater adsorbent which is low in development cost, environmentally friendly, nonpoisonous and harmless.