The invention relates to a preparation method of an ultra-high strength
spring steel having high
plasticity. The preparation method of the ultra-high strength
spring steel having the high
plasticity includes: when designing
alloy compositions of the
spring steel, adding moderate
alloy elements V and Nb based on the 55SiCr steel sort, and enabling the spring steel to contain 0.1-0.25wt% of the V and 0.005-0.03wt% of the Nb; in a heat treatment process, first performing austenitizing treatment on the spring steel workpiece, and then performing
tin bath low temperature isothermal
quenching treatment, wherein conditions of the
tin bath low temperature isothermal
quenching treatment are as following: an isothermal
quenching furnace is heated to 235-250 DEG C, the spring steel workpiece after passing through the austenitizing treatment is placed in the isothermal quenching furnace, a
tin bath is used as the isothermal quenching furnace, quenching speed is 200-300 DEG C.s<-1>, the spring steel workpiece is fetched out after 30-480min of isothermal heat preservation, and then is cooled to
room temperature in water at 15-25 DEG C, and
cooling speed is 200-300 DEG C.s<-1>. According to the spring steel prepared by using the preparation method, tensile strength reaches above 2200MPa, the percentage of
area reduction reaches above 40%, specific elongation reaches about 16%, and the productof strength and
ductility reaches above 35GPa%. The spring steel can be used as automobile
suspension spring steel so as to improve running stationarity of automobiles and traffic safety and riding comfort of driving and riding personnel.