The invention discloses a low voltage cable fixing device of a buried transformer. The low voltage cable fixing device comprises a low voltage cable box, at least one layer of fixed supporting plate is arranged in the low voltage cable box, a supporting vertical rod is arranged on the fixed supporting plate, an elastic cable holding ring is fixedly installed on a top end of the supporting vertical rod correspondingly, an opening for causing a cable to conveniently come in and get out from the elastic cable holding ring is formed in one side of the elastic cable holding ring, an cable dismounting auxiliary device for conveniently dismounting cables is arranged in the elastic cable holding ring, and an auxiliary locking device corresponding to the cable dismounting auxiliary device is arranged on an outer side of the elastic cable holding ring. According to the low voltage cable fixing device disclosed by the invention, the cables are fixed by the fixed supporting plate, the elastic cable holding ring and the supporting vertical rod, the cable fixing efficiency can be effectively improved, the use cost can be reduced, and the release of the auxiliary locking device applies an outward thrust to the cables, thereby facilitating the fast dismounting of the cables, and thus the use is more labor-saving.