Objective To analyze correlationship between transverse diameter, longitudinal diameter, and the longest diameter of small upper ureteral stones (transverse diameter ≤0.6 cm and longitudinal diameter ≤1.0 cm) and clinical events or factors and provide evidences for the treatment of patients with small upper ureteral stones. Methods A total of 56 patients with small upper ureteral stones (transverse diameter ≤0.6 cm and longitudinal diameter ≤1.0 cm) who were treated by ureteroscope were selected. Patients were divided into groups according to transverse diameter <0.5 cm and ≥0.5 cm, transverse diameter ≤0.5 cm and >0.5 cm, transverse diameter ≤0.55 cm and >0.55 cm, longitudinal diameter ≤0.6 cm and >0.6 cm, longitudinal diameter ≤0.5 cm, and >0.5 cm, the longest diameter ≤0.6 cm and >0.6 cm, the longest diameter <0.6 cm and ≥0.6 cm, and ratio of transverse diameter and longitudinal diameter ≤1 and >1. The differences of stone history, course of disease, displacement, symptom of pre-operative waist pain, degree of hydronephrosis, combined ureteral ureterostenosis, combined ureteral polyp, combined ureteral ureterostenosis or polyp, and success rate of ureteroscopic treatment of groups were compared and the linear correlation between transverse diameter and longitudinal diameter was studied. Results For the transverse diameter <0.5 cm group (n=21) and transverse diameter ≥0.5 cm group (n=35), the differences of course of disease, combined ureteral ureterostenosis, and combined ureteral ureterostenosis or polyp were statistically significant (P<0.05 or P<0.01). For the transverse diameter ≤0.5 cm group (n=31) and transverse diameter >0.5 cm group (n=25), only the difference of combined ureteral ureterostenosis was statistically significant (P<0.05). For the transverse diameter ≤0.5 cm group (n=24) and transverse diameter >0.5 cm group (n=32), and the longest diameter <0.6 cm group (n=23) and the longest diameter ≥0.6 cm group (n=33), only the difference of course of disease was statistically significant (P<0.05). For the transverse diameter ≤0.55 cm group (n=42) and transverse diameter >0.55 cm group (n=14), longitudinal diameter ≤0.6 cm group (n=37) and longitudinal diameter >0.6 cm group (n=19), the longest diameter ≤0.6 cm group (n=36) and the longest diameter >0.6 cm group (n=20), and ratio of transverse diameter and longitudinal diameter ≤1 group (n=31) and ratio of transverse diameter and longitudinal diameter>1 group (n=25), the differences of all items were not statistically significant (P>0.05). The rate of patients with no stone displacement and the course of disease ≤10 d of the transverse diameter <0.5 cm group was higher than that of the transverse diameter ≥0.5 cm group (P<0.05), and patients were all combined with ureteral ureterostenosis or polyp and the transverse diameter linearly correlated with the longitudinal diameter. Conclusion The transverse diameter, rather than longitudinal diameter or the longest diameter, is the simplified measure index with important clinical significance for the treatment of small upper ureteral stones. For upper ureteral stones with transverse diameters <0.5 cm, the main factor is mechanical obstruction that is irrelevant to the stone volume and no stone displacement in a short period of time (10 d) can be considered as one of intervention indications. Ureteroscope is important for examination and treatment.