Abstract : Objective To investigate the ffects of high concentration of semen samples in detection by fully automated sperm quality analyzer for sperm concentration, progressive motility ( PR) , non-progressive motility (NP ) and percentage of immotile sperm ( IM). Methods The semen samples from the patients who visited the reproductive clinic in our hospital from February 2023 to May 2023 were analyzed using the fully automated sperm quality analyzer. A total of 155 semen samples with initial sperm concentration ≥100x10*/mL and semen volume≥1.5 mL were set as the high concentration semen group ( group A). The semen samples with self seminal plasma dilution group (group B) and 37 C normal saline dilution group ( group C) were prepared with their own seminal plasma and normal saline at 1 :2 dilution ratio respectively. The sperm concentration of group A was detected by the manual method as the control.The sperm concentration and motility parameters of each group were detected. The diferences of sperm concentration and the values of PR, NP and IM among the group A, B and C were analyzed. The corelations between sperm concentration and PR, NP and IM were also assessed. Results The sperm concentration of group A was significantly lower than that of the control group and groups B and C (all P<0.05). There was no satistically significant diference for the results between group B and group C (P>0.05). The PR in group C was significantly lower than that in groups A and B ( all P<0.05) , and there was no significant difference of PR between group A and group B (P>0.05). The values of NP in group A was significantly higher than that in groups B and C (all P<0.05), and there was no significant difference in NP between group B and group C (P>0.05). The IM in group A was significantly lower than that in groups B and C (all P<0.05), and there was no statistical difference of IM values between group B ang group C ( P>0.05). Conclusion The direct analysis of undiluted semen samples with high sperm concentration may lead to lower results of sperm concentration, increased percentage of NP sperm and decreased percentage of IM sperm. The dilution of semen samples may improve the acuracy of the detection results. The dilution with 37 C normal saline can lead to decrease of the percentage of PR sperm. The self seminal plasma should be recommended as the first choice of diluent for the semen samples with high sperm concentration.