BackgroundChina has the largest number of individuals with type 2 diabetes mellitus (T2DM) in the world, and most lack knowledge about glycemic control and health management. This trial will examine whether a smartphone application can improve blood glucose management among individuals with T2DM.MethodsThis will be a 2-center, factorial design, equal proportional distribution, superiority trial conducted in outpatient endocrinology clinics at two tertiary hospitals in Chengdu, China. The trial will enroll smartphone-literature individuals at least 18 years old who have been diagnosed with T2DM based on glycosylated hemoglobin (HbA1c) of at least 7.0%. Individuals will be randomly assigned to receive routine care with standard education about T2DM and glycemic control (Control), routine care as well as weekly telephone reminders to self-monitor blood glucose (Reminder), routine care and a smartphone application providing information about glycemic control and health management with T2DM (App), or the combination of routine care, the smartphone application, and weekly telephone reminders (App + Reminder). After 6 months of these interventions, participants will be analyzed for the primary outcome of HbA1c as well as the secondary outcomes of blood glucose monitoring frequency, body mass index, blood pressure, knowledge about diabetes, health beliefs related to diabetes, diabetes self-management behavior, and satisfaction with the smartphone application.DiscussionThis trial will determine whether a smartphone application can improve glycemic management among Chinese with T2DM. The findings may help guide the development of effective applications in China and elsewhere.Trial registrationRegistration in the Chinese Clinical Trial Registry (ChiCTR) under registration number ChiCTR2100042297: https://www.chictr.org.cn/bin/userProject. 17 January 2021.