I. What is oligozoospermia? Oligozoospermia is defined as sperm concentration or/and sperm viability below the standard value. Due to the differences in semen testing methods and inconsistencies in reference standards among domestic laboratories at present, there are certain differences in the diagnosis of oligozoospermia. Although some laboratories have referred to the latest WHO 5th edition criteria, considering the current status of domestic laboratory tests and the reality of computer-aided analysis, most scholars still recommend using the WHO 4th edition criteria, i.e. sperm concentration <20×106/ml, total viability <70%, a <25% or a+b <50%. However, for sperm morphological testing, the 5th edition criteria were adopted and the lower limit of normal reference value was 4%. WHO Laboratory Test Manual for Human Semen (5th edition) The lower limit of the main reference value of semen II. To confirm the diagnosis of oligozoospermia, semen concentration and viability are important reference indicators, but only if the semen examination meets certain requirements. 1. Abstinence time: The length of abstinence can affect the judgment of oligozoospermia. Generally speaking, 3-5 days before the sperm examination without ejaculation (including ejaculation and seminal emission), too long may affect the vitality of sperm, too short may affect the concentration of sperm. 2. Number of examinations: Since sperm concentration and viability are inherently volatile, one examination does not fully reflect the overall situation, and it is recommended that the quality of sperm be objectively evaluated only after 2-3 standard examinations. 3. Sperm collection precautions: Before semen examination, you should try to avoid the following conditions: ① cold or fever; ② urinary tract or reproductive tract infection; ③ sauna or hot spring; ④ heavy smoking and alcohol abuse; ⑤ recent consumption of large amounts of drugs; ⑥ recent exposure to toxic substances or radiation.