Abstract: A DNA methyltransferase is derived from Deinococcus radiodurans and has a typical conservative structural domain of DNA methyltransferase. The DNA methyltransferase includes: an AdoMet binding region containing a “FxGxG” conservative sequence, a target sequence recognition region and a catalytic region containing a “TSPPY” conservative sequence sequentially from N-terminal to C-terminal; and belongs to ?-type DNA methyltransferase category. The recognized substrate DNA conservative sequence is 5?-CCGCGG-3?, a methylation modified position is N4 site of second cytosine to generate a 4mC type modified base, and an optimum temperature for methylated reaction is in a range of 25-37° C. The DNA methyltransferase can specific-recognize the conservative motif of “CCGCGG” and methylate the N4 site of the second cytosine to produce the 4mC modified base, which is a N4-Cytosine DNA methyltransferase.