Abstract: Dynamic segmentation model to divide bottom hole net pressure curve into different stages based on slope of curve includes: step S1, establish calculation model of bottom hole net pressure: according to wellhead pressure during hydraulic fracturing in shale gas reservoir, calculate bottom hole net pressure based on fluid dynamics theory; step S2, establishing dynamic segmentation model to divide bottom hole net pressure curve into different stages based on slope of curve by numerical analysis theory; step S3, establish recognition model to recognize extension behavior of underground fracture network based on rock mechanics and fracture mechanics; and step S4, combine step S1, S2, and S3 to realize automatic diagnosis for wellhead pressure curve of hydraulic fracturing in shale gas horizontal well. A diagnosis and analysis method of the wellhead pressure curve of hydraulic fracturing in shale gas horizontal well is described.