Method for controlling a step motor, wherein at least one phase winding has a short circuit state in the holding phase of the step motor; during a startup phase, wherein when the the step motor is started, an initial speed of the rotor is not zero or/and an initial position deviates from an equilibrium position, the method comprises controlling the step motor to perform following operations: setting a start frequency; calculating a total equivalent static load T L ' at an initial speed ω 0 and an initial position θ 0 by T L '=T L +T L1 +T L2, wherein T L is a load torque of the step motor at the time of static starting in an equilibrium position; an effect of the initial speed is equivalent to an initial speed equivalent load torque T L1, T L1 = -Jω 0 /t 1, where J is a rotational inertia, and t 1 is the time consumed from the initial position to a new equilibrium position, and an effect of the initial position is equivalent to an equivalent load torque T L2 of the initial position, T L2 =T L θ 0 /θ step, where θ 0 represents an initial position angle of the rotor and θ step represents a mechanical angle corresponding to one step of the motor; and according to the current starting frequency of the step motor and a static torque-frequency characteristic curve, obtaining the maximum startable static torque at the current starting frequency; comparing a total equivalent static load torque curve with the maximum startable static torque at the current starting frequency, wherein the total equivalent static load torque curve is obtained by calculating total equivalent static loads at different time points, by using the initial speed and initial position at each time point; if the maximum value of the total equivalent static load torque curve is less than the maximum startable static torque, starting the step motor at the total equivalent static load T L ' at the current frequency; and if the maximum value of the total equivalent static load torque curve is greater than the maximum startable static torque, a motor start failure alarm is issued. setting a start frequency; calculating a total equivalent static load T L ' at an initial speed ω 0 and an initial position θ 0 by T L '=T L +T L1 +T L2, wherein T L is a load torque of the step motor at the time of static starting in an equilibrium position; an effect of the initial speed is equivalent to an initial speed equivalent load torque T L1, T L1 = -Jω 0 /t 1, where J is a rotational inertia, and t 1 is the time consumed from the initial position to a new equilibrium position, and an effect of the initial position is equivalent to an equivalent load torque T L2 of the initial position, T L2 =T L θ 0 /θ step, where θ 0 represents an initial position angle of the rotor and θ step represents a mechanical angle corresponding to one step of the motor; and wherein T L is a load torque of the step motor at the time of static starting in an equilibrium position; an effect of the initial speed is equivalent to an initial speed equivalent load torque T L1, T L1 = -Jω 0 /t 1, where J is a rotational inertia, and t 1 is the time consumed from the initial position to a new equilibrium position, and an effect of the initial position is equivalent to an equivalent load torque T L2 of the initial position, T L2 =T L θ 0 /θ step, where θ 0 represents an initial position angle of the rotor and θ step represents a mechanical angle corresponding to one step of the motor; and according to the current starting frequency of the step motor and a static torque-frequency characteristic curve, obtaining the maximum startable static torque at the current starting frequency; comparing a total equivalent static load torque curve with the maximum startable static torque at the current starting frequency, wherein the total equivalent static load torque curve is obtained by calculating total equivalent static loads at different time points, by using the initial speed and initial position at each time point; if the maximum value of the total equivalent static load torque curve is less than the maximum startable static torque, starting the step motor at the total equivalent static load T L ' at the current frequency; and if the maximum value of the total equivalent static load torque curve is greater than the maximum startable static torque, a motor start failure alarm is issued.