Tanning process for multi-element chromium-free combined tanning cattle white wet leather and application of tanning process

The invention discloses a tanning process for multi-element chromium-free combined tanning cattle white wet leather. The tanning process comprises the following steps of tanning A, tanning B and tanning C. The tanning A comprises the following specific steps: controlling the liquid ratio in a rotary drum to be 0.3-0.5, adding 2-6% of a synthetic tanning agent, and conducting rotating; then adding 2-6% of a synthetic tanning agent, and conducting rotating; adding 30% of water, increasing the temperature in the rotary drum for the first time, and conducting rotating; and adding 30% of water, increasing the temperature in the rotary drum for the second time, controlling the pH value to 4.5-5.0, conducting rotating, and discharging liquid. The tanning B comprises the following specific steps: controlling the liquid ratio in a rotary drum to be 0.3-0.5, adjusting the pH value to be 4.0-4.5, adding 1-2% of dispersed tannin, 0.5-1.5% of grease and 0.1-0.3% of an auxiliary agent, conducting rotating, adding 5-15% of