Based on droplet microfluidics, we demonstrate a new method that can quantitatively measure the somatic cell count (SCC) of fat-free milk. A T-junction microdroplet generator is designed and monodisperse milk droplets can be produced in the T-junction microchannel by pressure-driven microfluidic flows. A mathematical model of the droplet length L_d/w_c as a function of the somatic cell count (SCC) is established. In particular, while monodisperse droplets are generated at low capillary numbers (Ca ≤ 0.1), a linear relation between L_d/w_c and 1/SCC is shown for different geometrical parameters of the T-junctions. Meanwhile, when the somatic cell count of the milk varies from 20 × 10⁴ mL⁻¹ to 300 × 10⁴ mL⁻¹, a linear relation is validated experimentally for a specific geometry of the T-junction. More importantly, by testing the length of the milk droplets, which are produced in the T-junction microdroplet generator, the somatic cell count of the milk can be quantified accurately. Additionally, the measuring precision of the milk's somatic cell count is studied experimentally for various geometries of the T-junctions.