Conventional semen PR21% means that the percentage of forward motion of sperm is 21%, which is lower than the normal reference value, and this index is used to detect whether the sperm motility is normal, reflecting the quality of sperm. Sperm motility refers to the ability of forward movement of sperm, which can directly reflect the quality of sperm, clinical work will be divided into 4 levels of sperm motility, in which PR, that is, forward movement belongs to a normal kind of movement, such as sperm movement is active and for a straight line or a large circle movement, the forward movement of a normal person should be ≥ 32%, and when the semen routine PR21% is lower than the normal reference value. When sperm motility is low, it is difficult to reach the fallopian tube or the combination with the egg is weak resulting in the inability to complete fertilization, suggesting that the sperm quality is not good, you need to clarify the cause of the disease under the guidance of the doctor, active treatment.