Schnorr was born at Leipzig, where he received his earliest instruction from his father Johann Veit Schnorr (1764 - 1841), a draughtsman, engraver and painter.

At seventeen he entered the Vienna Academy, from which Johann Friedrich Overbeck and others who rebelled against the old conventional style had been expelled about a year before.

In 1818 he followed the founders of the new artistic brotherhood, the Nazarene movement, in their pilgrimage to Rome. This school of religious and romantic art abjured modern styles and reverted to and revived the principles and practice of earlier periods.

At the outset an effort was made to recover fresco painting and monumental art, and Schnorr found opportunity of proving his powers, when commissioned to decorate with frescoes, illustrative of Ariosto, the entrance hail of the Villa Massimo, near the Lateran. His fellow-laborers were Cornelius, Overbeck and Veit.

His second period dates from 1825, when he left Rome, settled in Munich, entered the service of King Ludwig, and transplanted to Germany the art of wall-painting learned in Italy. He showed himself qualified as a sort of poet-painter to the Bavarian court; he organized a staff of trained executants, and set about clothing five halls in the new palace with frescoes illustrative of the Nibelungenlied. Other apartments his prolific pencil decorated with scenes from the histories of Charlemagne, Frederick Barbarossa and Rudolph of Habsburg. Critics considered these interminable compositions to be creative, learned in composition, masterly in drawing, but also exaggerated in thought and extravagant in style.

Schnorr's third period is marked by his Biblical illustrations. The artist was a Lutheran, and took a broad and un-sectarian view which won for his Pictorial Bible ready currency throughout Christendom. Frequently the compositions are crowded and confused, wanting in harmony of line and symmetry in the masses; thus they suffer under comparison with Raphael's "Bible". The style is severed from the simplicity and severity of early times, and surrendered to the florid redundance of the later Renaissance. Yet throughout are displayed fertility of invention, academic knowledge with facile execution.

Biblical drawings and cartoons for frescoes formed a natural prelude to designs for church windows. The painter's renown in Germany secured commissions in Great Britain. Schnorr made designs, carried out in the royal factory, Munich, for windows in Glasgow cathedral and in St Paul's Cathedral, London. This Munich glass provoked controversy: medievalists objected to its want of lustre, and stigmatized the windows as coloured blinds and picture transparencies. But the opposing party claimed for these modern revivals the union of the severe and excellent drawing of early Florentine oil-paintings with the colouring and arrangement of the glass-paintings of the latter half of the 16th century.

Schnorr died at Munich in 1872. His brother Ludwig Ferdinand (1789 - 1853) was also a painter. Julius's son (1836 – 1865), also called Ludwig was an operatic tenor, best known for being the first to sing Wagner's Tristan shortly before his death.