The invention discloses a multi-stage early-warning method based on well deflection. The multi-stage early-warning method specifically comprises the following steps that S1, well deflection data are extracted from data measured by while-drilling measuring equipment, and resampling is conducted to form equal-distance data; S2, a data sequence A:{dep,dev} is built according to a depth-numerical value mode; S3, according to an original designed track data sheet for well drilling, the sampling interval used in the step S1 is adopted to build a designed track data sequence B:{dep,dev}; S4, a parameter fdev is set as a well deflection deviation alarming threshold value; S5, according to the depth dep of a drill bit, the well deflection devs of a designed track at the drill bit is calculated; andS6, the difference ddev between the well deflection data of an actual track of the drill bit and the well deflection data at the corresponding position of the designed track is calculated. Through the well deflection multi-stage early-warning method, the deviation of the well-drilling track can be early warned in real time, manual detection work of guiding personnel is reduced, accidents are avoided, and the production cost is lowered.