To evaluate clinical efficacy of modified kidner procedure with tendoscopy in treating painful accessory navicular. From February 2014 to April 2019, 19 patients with painful accessory navicular were admitted, including 13 males and 6 females with a mean age of 26 years old (ranged from 14 to 58 years old), all of which were unilateral symptoms. The courses of disease ranged from 6 to 60 months. All patients received excision of accessory navicular and reconstruction of posterior tibial tendon insertion on navicular with anchor, and the tendoscopy were used to examin the posterior tibial tendon. American Orthopedic Foot and Ankle Society(AOFAS) midfoot score and visual analogue scale(VAS) were used to evaluate efficacy before operation and at the latest follow-up. All the patientswere followed up, and the duration ranged from 12 to 73 months, with an average of (35.0±20.9) months. VAS score was 0.20±0.41 at the latest follow-up, showing significant difference when compared with preoperative score of 6.33±1.95(t=11.50, P<0.01). AOFAS score was 95.53±5.79 at the latest follow-up, showing significant difference when compared with preoperative score of 60.27±21.51 (t=5.71, P<0.01). The modified kidner procedure with tendoscopy is a good choice for the treatment of painful accessory navicular, which could obviously relieve foot pain, improve foot function, and has certain clinical efficacy.