Objective  To investigate the safety of erythrocytapheresis in patients with high altitude polycythemia undergoing arthroplasty and the effectiveness of reducing the incidence of lower extremity deep vein thrombosis(DVT).Methods  A retrospective analysis was carried out focusing on the clinical data of 45 Tibetan male patients who underwent total hip arthroplasty(THA) and total knee arthroplasty (TKA) in the Department of Orthopaedics of our hospital from October 2018 to August 2020.Of the enrolled 45 patients，34 cases underwent THA and the other 11 cases were provided with TKA.The average age was (51.40±13.29) years old (ranging：31 to 73).The body mass index(BMI) was 21.79~33.79 kg／m²，with a mean BMI of (28.69±3.05) kg／m²；and the mean preoperative hemoglobin was (215.10±17.92)g/L，with a mean value of 191.00~249.00 g/L.In addition，the indication of preoperative therapeutic erythrocytapheresis was Hb>190g/L.Blood samples were taken for routine blood test prior to and on the second day of erythrocytapheresis，the first day and the third day after the operation to observe the changes of red blood cell count(RBC)，hemoglobin(Hb) and hematocrit(Hct).Meanwhile，D-Dimer was detected by blood sampling before erythrocytapheresis and the first day after operation to observe the change of D-Dimer.All patients were examined by color Doppler ultrasound of of veins of both lower extremities routinely for DVT screening before and 1，3，7，14，35 days after operation.Results  Routine blood test：RBC was tested to be(5.89~8.70)×10¹²/L and(3.84~6.63)×10¹²/L before and after erythrocytapheresis，with a mean value of (6.85±0.95)×10¹²/L and (5.30±0.75)×10¹²/L，respectively；besides，it was (3.21~6.18)×10¹²/L and (3.25~6.10)×10¹²/L one day and three day after operation，with the mean value of (4.76±0.89)×10¹²/L and (4.28±0.98)×10¹²/L，respectively.There was statistical difference between the values after single-harvest，postoperative day 1，postoperative day 3 and before single-harvest (P＜0.05).Hb was 191.00~249.00 g/L and 133.00~191.00 g/L before erythrocytapheresis and after erythrocytapheresis，with the mean Hb of(215.10±17.92)g/L and (167.60±16.26)g/L，respectively；in addition，it was 109.00~180.00 g/L and 108.00~175.00 g/L 1 day and 3 day after operation，with the mean Hb of(150.67±21.95)g/L and(133.00±24.15)g/L，respectively；and the difference was statistically significant between the values after single-harvest，postoperative day 1，postoperative day 3 and before single-harvest(P＜0.05).Hct was detected to be 57.70%~72.80% and 38.90%~57.30% before erythrocytapheresis and after erythrocytapheresis，with a mean value of (62.73±5.24)% and (49.45±4.93)%，respectively；and it was 32.10%~52.70% and 32.30%~50.20% one day and three day after operation，with the mean value of (44.11±5.94)% and (38.70±6.52)%，respectively，with statistically significant difference between the values after single-harvest，postoperative day 1，postoperative day 3 and before single-harvest (P＜0.05).2.D-Dimer was detected to be 0.01~1.20 mg/L and 2.37~6.07 mg/L before erythrocytapheresis and one day after operation，with the mean value of (0.28±0.45)mg/L and (4.04±1.54)mg/L，respectively；and the difference was statistically significant (P＜0.05).3.In terms of DVT，one patient was found to have thrombosis of bilateral posterior tibial vein，left fibular vein and calf intermuscular vein on the first day after THA.In addition，there was no cases of pulmonary embolism and blood transfusion. Conclusion  Erythrocytapheresis can be effective to reduce the incidence of DVT for the population with high altitude polycythemia in the perioperative period of arthroplasty.Besides，it is safe and reliable，exhibiting good clinical application value.