The invention provides a guy cable type spatial position measurement mechanism and method. The guy cable type spatial position measurement mechanism is characterized in that the guy cable type spatial position measurement mechanism comprises two measurement frames (1) arranged in parallel and a positioning shaft (6), two guy cable encoders (2) are symmetrically arranged on each measurement frame (1), two guiding pulleys (3) are symmetrically arranged on each measurement frame (1), two deflection compensation pulley supports (5) are arranged on each measurement frame (1), deflection compensation pulleys (4) are arranged on the deflection compensation pulley supports (5) respectively, four centripetal legs (7) are arranged on the positioning shaft (6), guy cables (8) in the four guy cable encoders (2) arranged on the deflection compensation pulley supports (5) are connected with the corresponding legs (7) on the positioning shaft (6) through the guide pulleys (3) and the deflection compensation pulleys (4), and the space coordinate of a measured point is obtained through mathematical calculation. The guy cable type spatial position measurement mechanism and method have the advantages of being simple in structure, convenient to assemble, easy to operate, high in precision and low in cost.