The m-sequences are popularly used in radar and communication systems because of its character of uniform auto-correlation sidelobes.The sidelobes of the m-sequences are not bilevel any more when the m-sequences are modulated by the symbols.Researches reveal that the sidelobes of the m-sequences can be greatly different given the same generator polynominal but different initial phase modulation. The ratio of mainlobes to sidelobes can be increased by choosing special initial phase modulation and even more increased when the mismatched filter is adopted. The features of the matched and mismatched filters are discussed when the inputting m-sequences are modulated by the symbols.