To analyze the characteristics of cloud condensation nodules (CCN) and aerosol particle size distribution and their influencing factors in the Middle Tianshan region of Xinjiang, aerosol and CCN number concentration data were measured using an aerosol wide-range particle size spectrometer and a Cloud Condensation Nodule Counter from August 4–25, 2019, and combined with meteorological element data and the HYSPLIT model for comprehensive analysis. The results show that during the observation period, the mean value of aerosol number concentration in Tianshan was 3607±4105cm-3, with the highest percentage of Aegean nuclear mode particles (64.76%). The mean values of CCN number concentration at 0.1%, 0.2%, 0.4%, 0.6% and 0.8% supersaturation were 185±185cm-3, 648±345cm-3,1576±1045cm-3, 2077±1417cm-3 and 2408±1657cm-3, respectively. The average spectral distribution of aerosol number concentration showed a unimodal distribution with peak particle size located at 29.5 nm. The diurnal variation of aerosol number concentration peaked at 08:00 (Beijing Time, the same below), 17:00 and 20:00, which was mainly affected by the diurnal variation of boundary-layer height, mountain-valley wind, emission sources, and other factors. The aerosol particles in the Tianshan mountains during summer were found to exhibit different modes of distribution. The Aitken mode particles displayed a bimodal distribution, while the accumulation mode particles had a trimodal distribution. The number concentration of nuclear mode particles showed a unimodal diurnal variation, which may be attributed to new particle formation. The CCN activation spectrum fitting result is N=3111S0.896 (N is the CCN number concentration at the supersaturation S), which is a clean continental type feature. The diurnal variation of CCN number concentration peaked at 08:00, 18:00 and 21:00. New particle formation (NPF) is beneficial to the increase of CCN number concentration at the mountain Tianshan. Under the supersaturation of 0.1%, 0.2%, 0.4%, 0.6% and 0.8%, the average concentration of CCN in NPF day is 13%, 18%, 25%, 22% and 20% higher than that in the non-NPF day, respectively. The relative humidity (RH) has a greater impact on the concentration of nucleation mode particles and a smaller impact on the concentration of other mode particles. As RH increases, the aerosol size distribution shifts towards larger particle sizes. When RH>60%, the number concentration of aerosol and CCN decreased with increasing RH. The aerosol and CCN number concentrations are higher under northerly and easterly winds due to the influence of topography and valley winds. There are four main types of air masses in Tianshan: western (29.2%), northwestern (29.3%), northeastern (27.0%), and southern (14.5%). The aerosol number concentration of the northeastern air mass from the northern Tianshan Mountains is the highest at 5449±3793cm-3 and the lowest at 1971±2087cm-3 due to the different direction and movement path of the air masses and the influence of the northern urban zone. The northeastern air mass has higher CCN number concentrations at all supersaturation levels, which are 100%-150% higher than the lowest southern air mass.