The present invention provides a retractable frame of a projection screen, which comprises: a receiving case; a rolling shaft; a rolling device; a first support rod having one end laterally extended with an engaging plate having a plate hole, two opposing sides of the engaging plate respectively having an engaging surface; a second support rod having one end extended with two engaging arms, and each engaging arm having an engaging hole; a combination member connected with the second support rod and the first support rod; a top supporter; and a projection screen. When being unfolded, the top supporter is upwardly pulled till the connection location of the second support rod and the first support rod being approximately a line, so the engaging arms can be tightly abutted against the end portions of the engaging surfaces for achieving the objective of support.