Mn-doped all-inorganic perovskite quantum dots (QDs) provide prominent applications in the fields of low-cost light source or display, because of their remarkable properties including dual-color emission and reduced lead content, as well as high photoluminescence quantum yields (PLQYs) and high stability. However, the existing synthesis approaches usually require hash conditions, such as high temperature and nitrogen protection, which is a major hurdler for the practical manufacturing. In addition, the significantly high Mn substitution ratio in CsPbX₃ QDs is still challenging. The real dual-color emission with two strong emission peaks in the Mn-doped all-inorganic perovskite QDs has attracted great interest. Here we present a gram-scale approach to synthesize both CsPb_xMn_1−xCl₃ and CsPb_1−xMn_xCl_yBr_3−y QDs at 100 ℃ in the air with high Mn substitution ratio, up to 55.64% atomically. The as-prepared CsPb_1−xMn_xCl_yBr_3−y QDs exhibit high PLQYs of 62.41% and dual-color emission with two strong emission peaks around at 400–450 nm and 600 nm, respectively. The enhanced peak at 400−450 nm is a result of the hybrid halides in CsPbBr_xCl_3−x host. Furthermore, the unique advantage of the optical emission and high PLQYs properties of the CsPb_xMn_1−xCl₃ QDs has been demonstrated as invisible ink for encryption applications and polymer composites. Our gram-scale synthesis approach for Mn-doped all-inorganic perovskite QDs may boost the future research and practical applications of QDs-based white LED, spintronics, and molecular barcoding.