Aquarius is most compatible with Libra and Gemini. Aquarians also relate very well with Sagittarius and Aries. They are less likely to be friends or partners with Cancer and Virgo. Aquarius is least likely to be compatible with Scorpio and Taurus.
This kind of reasoning is based on Sun sign astrology. It can be helpful to a degree. But it's inaccurate much of the time. It's based on less than ten percent of the information that you would need to evaluate the likelihood of astrological compatibility between two people.
If your Sun sign is in Aquarius and you are in a happy love relationship with a Taurus there is probably a good underlying astrological basis to this compatibility. As an example, your Moon might be in Taurus. And your partners Ascendant may be in Aquarius conjunct your Sun.
There are several key indicators of compatibility between two people. Firstly the indicators will be different and have different weights depending on whether you are looking at long-term love, a passionate fling or compatibility between friends or co-workers.
The aspect that most signifies true and lasting compatibility between two lovers is the Sun/Moon connection.
The coming together of the Sun and Moon is essentially the astrological definition of marriage. It is the unity of masculine and feminine energies. Here the conjunction is strongest, the trine is also very powerful, the opposition can be positive but the square is usually detrimental.
If an Aquarian male is born on February 3rd for example, his Sun will be in the middle of the Aquarius sign. He will naturally feel at home with any woman who has her Moon in Aquarius (and particularity in mid Aquarius). The tighter the aspect, the more compelling will be the mutual attraction and harmony. He will also feel an instant attraction for women with Moons in Gemini and Libra, and often Leo. The tighter the trine or opposition, the stronger the attraction.
Aquarian females can see where the Moon is located in their natal charts. If it's in Virgo for example, this will explain why you may often find yourself deeply connected to Virgo males, though this would not be explained by Sun sign astrology.
For magnetic or sexual attraction indicators, look to the aspects that are made between Mars and Venus in the two birth charts. The conjunction is the most powerful, but oppositions, squares and trines are also strong indicators of a magnetic, physical attraction between two people. Other strong indicators are Venus/Uranus and Venus/Pluto aspects between two charts.
This is a brief and incomplete overview of some of the key compatibility aspects. To find out compatibility potential based on a real astrological analysis you would need to compare the two birth charts. You can do this for free at several online sites.
The above fine art print is "Tendresse" by Claude Theberge. See at AllPosters.com.