The invention discloses a laser distance measuring method and system based on pulse counting and time expansion. The method includes the steps that a laser scanner is arranged above an object to serve as a coordinate original point, a three-dimensional right-angle coordinate system is built, the tail end of the laser scanner serves as a fixing point, the object rotates with the radius gradually changing, a direction vector, the emission moment and the receiving moment of an emitted laser pulse signal are recorded, flight time of the laser pulse is obtained according to the emission moment and the receiving moment, optimization is carried out through a pulse counting method and a time expansion method, optimized flight time is obtained, the distance between the laser scanner and an measured object is solved according to the optimized flight time, and horizontal distance of the measured object and the object is solved.