Here's the deal. Getting up to a 500 pound deadlift can generally be done fairly quickly. Developing a big squat generally takes much longer. Squatting is much more of a skill that just takes more hours to learn.
For example, I had similar numbers to yours, when I hit a 500 pound deadlift I had about a 315 pound squat, if that. Fast forward a couple of years and I got up to a 565 deadlift and a 500 pound squat.
When you start out, most people can pull far more than squat. The longer you train, the more your squat will generally catch up.
Another thing to consider is your size, weight, and build. Smaller guys generally have big pulls and much smaller squats. The bigger you get, the more even those numbers get (or squats can even pull ahead). You may also be built better for pulling.
All that said and considered, check your squat technique.