The invention discloses a chrome-free metal compound tanning agent which comprises the following components in percentage by weight: 60.0%-75.0% of zirconium sulfate, 10.0%-15.0% of aluminum sulfate, 10.0%-15.0% of titanyl sulfate and 5.0%-10.0% of sodium aluminum silicate. The invention further discloses a preparation method of the chrome-free metal compound tanning agent. The chrome-free metal compound tanning agent provided by the invention is good in comprehensive performance, simple in production process and environment-friendly; the preparation method of the environment-friendly chrome-free metal compound tanning agent is simple; in addition, the chrome-free metal compound tanning agent is good in compatibility with existing leather-making materials and easy to popularize.