The Orto-Koi-Suu river basin, Kungey Ala-Too range in the Northern Tien Shan in the Kyrgyz Republic hosts 15 glaciers, with a total area of ~ 6.52 km² (in 2024) and extends over an altitude of 3700 to 4400 m a.s.l. The glaciers in the Orto-Koi-Suu basin have lost an average of about 140 m in length and 1.61 km² in area over the entire period from 1990 to 2024. Glacier No. 599, has been monitored using the glaciological method to calculate the mass balance since 2014 to the present. Annually 10 to 12 ablation point observations and two snow pits, as well as glacier tongue position have been measured. Annual mass balance calculations with direct glaciological method suggest an average annual mass balance of -0.44 m w.e. yr-1 (2014-2024). However, in recent years we have observed the trend of increasingly negative annual mass balance. This corresponds well to reported mb gradient rotational shift at the Golubin glacier (Azisov et al 2022) We further simulated the glacier mass balance from 2000 to 2025 and estimated the glacier runoff in the Orto-Koi-Suu river basin. Our preliminary results suggest an equilibrium line altitude for the whole period of 4138 m a.s.l. and a hydrological mass balance of -0.48 m w e yr-1.