The invention discloses a TRIP (transformation induced plasticity) steel plate containing rare earth La and a preparation method of the TRIP steel plate. The steel plate comprises chemical ingredients in percentage by mass as follows: 0.15%-0.3% of C, 1.0%-3.0% of Mn, 0.05%-0.15% of P, smaller than 0.3% of Si, 0.5%-3.0% of Al, 0.005%-0.02% of La and the balance of Fe and other unavoidable impurities. The preparation method of the TRIP steel plate comprises steps as follows: a steel billet is heated to the temperature of 1,150-1,250 DEG C with a furnace, subjected to thermal insulation for 1.5-3 hours and then subjected to hot rolling, the initial rolling temperature of rough rolling is controlled in the range of 1,050 DEG C-1,110 DEG C, the final rolling temperature of finish rolling is controlled in the range of 860 DEG C-900 DEG C, and the simulating coiling temperature is controlled in the range of 500-600 DEG C; cold rolling is performed after hot rolling, and thermal treatment is performed; and the tensile strength of the steel plate is larger than 780 MPa, and the elongation percentage is larger than 24%.