OBJECTIVE:To compare antidiuretic activity of Ootheca Mantidis before and after processing,and to explore the best medicinal part and mechanism of Ootheca Mantidis. METHODS:96 rats were randomly divided into blank group,model group,positive group,Ootheca Mantidis group,Ootheca Mantidis stir-fried with salt group,steamed Ootheca Mantidis group, crude product eggs and egg shell groups,processed product eggs and egg shell groups,with 8 rats in each group,12 groups in to-tal. Except blank group,other groups were given adenine 250 mg/kg,ig,for 4 weeks to induce kidney-yang and diuresis model. From third week,Ootheca Mantidis crude drug group and processed Ootheca Mantidis group were all given relevant medicine 0.11 g(crude drug)/ml i.g,and crude product eggs and egg shell groups and processed product eggs and egg shell groups were given rel-evant medicine,ig,once a day,by mass ratio of eggs to egg shell(cude drug 1∶2.4,salt stir-fried product 1∶1.7,steamed prod-uct 1∶2.1)for consecutive 4 weeks. The urinary volume,body weight,renal index and the serum contents of ADH and ALD were all determined. RESULTS:Compared with blank group,body weight and serum content of ADH and ALD decreased in model group,while renal index and urinary volume increased(P<0.05). After 4 weeks of treatment,compared with model group,body weight and serum content of ADH increased in Ootheca Mantidis groups,while urinary volume and renal index decreased (P<0.05);serum content of ALD increased in treatment groups;there was statistical significance in the serum content of ALD in those groups except Ootheca Mantidis group,Ootheca Mantidis stir-fried with salt group and steamed Ootheca Mantidis group (P<0.05);except for ALD,those index were in descending order of steamed Ootheca Mantidis group>Ootheca Mantidis stir-fried with salt group>Ootheca Mantidis group,and steamed Ootheca Mantidis shell group had best exchange. CONCLUSIONS:The an-tidiuretic activity of Ootheca Mantidis has been enhanced after processing. The egg shell of steamed Ootheca Mantidis is main me-dicinal part. To increase the serum content of ADH might be one of the main mechanism of arresting polyuria.