The slot-die coating & calcination process was adopted to fabricate the long YBCO precursor films on the buffered metal tape for the $2^{nd}$ generation coated conductors. To obtain the smooth and crack-free surface of long YBCO precursor films, the parameters of slot-die coating and the process variables of calcination step must be optimized simultaneously in reel-to-reel method. Among the parameter of slot-die coating process, the viscosities of the precursor solution was controlled from 60cP to 200cP to obtain the thicker films from on single coating. The slot-die gap, the injection rate of precursor solution, the moving speed of buffered metal tape etc. are controlled lot the full coverage and smooth surface of YBCO precursor films. The slot-die coated films are moved through the tube furnace with predetermined heating profiles in humid oxygen ambient The YBCO precursor films was identifed with $Y_2O_3,;BaF_2$, and CuO phase by XRD and consisted of fine grains of about 20nm size observed by FE-SEM. The YBCO films show the critical current density over $MA/cm^2$ using the precursor films formed by the continuous slot-die coating & calcination process.