A wireless transmission expansion device includes: an expansion unit having a bottom base portion, the bottom base portion having therein a receiving space, wherein each of two sides of the bottom base portion extends to form a positioning clamping arm, and the two positioning clamping arms define therebetween a clamping space; a wireless transmission device disposed in the receiving space; and at least one antenna module disposed at the positioning clamping arms and being in signal connection with the wireless transmission device. Therefore, the wireless transmission expansion device operates in conjunction with an existing video apparatus or portable camera not capable of 4G transmission or not having internal storage space required for 4G transmission, so as to instantly transmit a large amount of video information.