Platelet-rich plasma therapy (PRP) is a new method for the treatment of partial rotator cuff tear, including partial supraspinatus tear. Aims: To assess the effectiveness of ultrasound-guided injection of PRP in the treatment of partial supraspinatus tear and evaluate adverse effects of this therapy after 12 weeks of follow-up. Methods: Controlled clinical trials were followed up to 12 weeks in 40 patients (42 tendons) partial supraspinatus tear received three,every 3 weeks, ultrasound-guided injections of PRP into the supraspinatus tendon. Results: After 12 weeks of treatment, there was an improvement in VAS, abduction angle of the shoulder joint, and SPADI scores in the research group: The average VAS and SPADI scores were decreased from 6,74 ± 0,96to 3,07±1,87 points and from 59,14 ± 8,7 to 27,61 ± 16,1 points, the average abduction angle of the shoulder joint was increased from 70,23 ±18,54 degrees to 130,4 ± 38,2 degrees (p < 0,05). Side effects of the research group were 57,1% of the patients increased pain at the injection site over 24 hours, 4,7% feeling hot and there was no serious complication in the group. Conclusion: ultrasoundguided injection of PRP is good at the treatment of partial supraspinatus tear and this therapy is safe