In order to decrease microfluidic analysis cost, a smartphone-based method for detecting the position of a droplet on piezoelectric substrate is presented, An application soft is developed for sensing droplet position, which can be obtained by analyzing its color information and geometry information, In the meantime, transportation velocity of the droplet is calculated by help of the interesting time, A 5 μL black ink solution droplet is used to demonstrate the utility of the presented method, The results show that the droplet on the piezoelectric substrate can be identified and its position can be determined using the self-developed app, The average transportation velocity of the droplet is 0, 416 mm/s from 2 s to 10 s at 27, 5 dBm of signal power,