The utility model discloses a city rail straight line traction motor, its constitution is: by excitation winding (1) of a plurality of runway molded liness circle of high temperature superconducting materia lap wound on coil skeleton (2) as the motor, fix in low temperature container (3) that link to each other with secondary skeleton (4), the motor rotor automobile body leans on the support column to link to each other with track (7), excitation winding (1) connect with superconductive switch (8) parallelly connected excitation current of access, utilize superconductive switch (8) from normally realizing the closed loop constant current of excitation winding (1) to the conversion of superconducting state. Star or delta connection are adopted around on primary iron core (6) in copper three -phase symmetry primary winding (5), the three -phase symmetry alternating current lets in and after, will produce three -phase travelling wave magnetic field in air gap department, with the strong magnetic field that high -temperature superconductor excitation winding (1) produced, realize linear electric motor's high thrust operation. The utility model is used for aspects such as urban rail transit have broken through on -vehicle excitation power source's constraint, have advantages such as light in weight, thrust density is high, the work air gap is big.