Abstract: Series continuous annealing water quenching tests were completed for 0.18C-0.4Si-2.0Mn microalloyed cold rolled ultra high strength steel strip on the test bench, the microstructure and tensile properties were studied. The results show that the holding time had a significant effects on microstructure and tensile properties when the holding temperature was below 800 ℃ and the microstructure was mainly lamellar martensite, when the holding temperature was higher than 830 ℃, the holding time showed less effects on tensile strength and elongation, and the microstructure was mainly lath martensite. With the increase of holding temperature and water quenching temperature, the tensile strength increased from 1 150 MPa to 1 700 MPa, yield strength increased from 600 MPa to 1 600 MPa and the elongation reduced from 8.5% to 2% gradually. When the holding temperature and water quenching temperature was 830 ℃ and 750 ℃, or holding temperature was 850 ℃ and water quenching temperature was higher than 700 ℃, the tensile strength was higher than 1 500 MPa and yield strength up to 1 200 MPa at the same time.