The 5-year-old gelding, Uncontainable, was "humanely euthanized" after suffering a fractured right front ankle, according to an incident alert on the race track's website.
Another horse, a 6-year-old gelding named Harliss, was also euthanized Friday after fracturing his right front ankle during a race, bringing the total number of horse deaths to 41 since December 2018.
They marked the 2nd and 3rd deaths during the latest racing season the park.
Animal rights activists were expected to demonstrate at the park Sunday afternoon.
The season opened late last month with the news of the death of 3-year-old gelding named Truest Reward after sustaining an injury while training.
As new season opens, another horse dies at Santa Anita - 38th death in the past year
As new season opens, another horse dies at Santa Anita - 38th death in the past year