The invention discloses a control method for a matrix frequency converter during supply of a DC source. Under the condition of the supply of the DC source, a positive pole and a negative pole of the DC source are respectively connected to three input ends of the matrix frequency converter correspondingly, namely an R input end, an S input end and a T input end; and the matrix frequency converter converts DC into AC to drive a motor to work. The control method can control the motor to normally work by adopting the DC source under the condition that a three-phase AC source is powered off.