The 20th-ranked Aztecs entertained a neighboring San Diego school that is in its first season playing NAIA basketball.
San Diego State scored the game's first 13 points, built a 27-3 lead and was out front at halftime 63-17.
Dwyane Polee added 19 points from off the bench and San Diego State's substitutes totaled 60 points.
San Diego State improved to 10-1, hitting 61 percent from the field and making 18-of-32 from 3-point range.
St. Katherine (1-10) was led by nine points from Joshua White. The Firebirds attempted 38 shots from beyond the arc and made just three of them.