A toy gun gas intake control mechanism (D) includes a holder frame (1), an impact member (2) having an elongated base (21) pivoted with its bottom end to the holder frame (1), a striking block (22), a pivot axle (24) that pivotally connects the striking block (22) to the top end of the elongated base (21) and a first spring member (51) for revering the striking block (22), a retaining block (4) supported on a second spring member (52) in the holder frame (1) and having a retaining notch (41) for retaining the outer end (241) of the pivot axle (24). When firing a bullet, the bolt body (C) of the toy gun moves forwards, the striking block (22) strikes a seal member (B1) to open a gas inlet (C11), and the pivot axle (24) is moved out of the retaining notch (41) of the retaining block (4) for allowing upward displacement of the retaining block (4). When the bolt body (C) moves backward after firing, the retaining block (4) is forced downwards to the inside of the holder frame (1) by the bolt body (C), the outer end (241) of the pivot axle (24) is engaged into the retaining notch (41), and the striking block (22) is returned, causing the seal member (B1) to close the gas inlet (C11) again.