http://forums.whirlpool.net.au/archive/1460568
很多辦法。不少人用 cayenne and/or pepper。
http://pets.thenest.com/can-mix-keep-cats-urinating-property-8268.html
The Porch
As soon as you finish sandblasting and refinishing your front porch, the neighborhood tomcat comes over and lifts his leg on every corner. You get a whiff of his "perfume" every time you open the window. The first step is cleaning the area thoroughly. Pick up a bottle of enzymatic cleaner from your local pet store. These specialized cleaners break up the enzymes in cat urine that make the area smell like a toilet to animals, even if you constantly clean. Once the urine smell dissipates, fill a spray bottle with white vinegar. If the smell of vinegar bothers you, dilute it with water and make a 50:50 vinegar-water batch. Spray all of the corners of your porch, including underneath. The vinegar smell repels the neighborhood feline gang.
https://www.yelp.com/topic/oakland-how-do-i-stop-a-cat-from-urinating-on-my-front-door