Abstract: Coal geological strength index （GSI） is an important parameter in coal mine engineering,which reflects the stability of coal strength. This paper uses Android Studio software to develop and design a coal geological strength index （GSI） detection system based on Android mobile platform. After the coal sample is made into the coal core of the corresponding specification,the coal pictures are taken by mobile phone or photo album,and then the coal fracture image is obtained after image processing,and then the GSI value can be calculated by processing the coal fracture image according to the fractal dimension,and the detection results can be displayed in real time. Using Java language and OpenCV computer vision library to realize coal GSI image processing and detection on Android mobile phone. The results show that the GSI value obtained by the system has a linear fitting relationship with the actual value,and the error is small,the detection time is less than 5 seconds,which greatly shortens the time of GSI value determination,reduces the difference of traditional manual measurement,and has a certain practical application value for coal exploration and mining.