The invention discloses a direct torque control method based on duty cycle control, which comprises the steps of S1, collecting data of the rotation speed [omega], rotation angle [theta] and three-phase current isa, isb and isc of a motor; S2, converting the three-phase current isa, isb and isc into a rotating coordinate system to obtain current isd and isq; S3, calculating the electromagnetic torque Te, d-axis flux linkage [psi]d, q-axis flux linkage [psi]q and amplitude [psi]s of the stator flux linkage; S4, calculating a sector in which the stator flux linkage is located; S5, calculating areal-time stator flux linkage instruction value, and acquiring a torque reference value according to rotation speed PI control; S6, selecting a voltage vector ui by using a table lookup method; S7, calculating an included angle [theta]psid between the stator flux linkage at the current moment and the d-axis at the action moment; S8, calculating an included angle [theta]ud between the effective voltage vector ui and the d-axis at the action moment according to the selected effective voltage vector ui, the rotation speed [omega]r, the rotation angle [theta]r; and S9, calculating the duty cycle hof the selected effective voltage vector, and calculating the input pulse of each switch tube of an inverter. The direct torque control method improves the calculation method of the duty cycle, and can effectively reduce the amplitude of harmonic components of the torque and rotation speed in a low frequency band.