The present disclosure provides a Cas12i protein comprising an amino acid sequence having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identity with the amino acid sequence represented by any one of SEQ ID NO: 1-10 (preferably, SEQ ID NO: 1-3 and 6, more preferably, SEQ ID NO: 1). The present disclosure also provides an engineered, non-naturally occurring CRISPR-Cas system comprising: (1) the Cas12i protein or a polynucleotide encoding the Cas12i protein; and (2) a CRISPR RNA (crRNA) or a polynucleotide encoding the crRNA, the crRNA comprising: (i) a spacer sequence capable of hybridizing to a target sequence of a target DNA, and (ii) a direct repeat (DR) sequence linked to the spacer sequence capable of directing the binding of the Cas12i protein to the crRNA to form a CRISPR-Cas complex that targets the target sequence.