Wind tunnel tests were carried out to study the wind pressure on principal square building adjacent to another one in tandem. The interference effects on local pressure of the principal building were analyzed with different positions and heights of interfering building. It is shown that as height ratio is fixed, mean pressures on windward face are suctions when spacing ratio is less than 3, otherwise they are positive. The magnitudes of mean suctions on the side and leeward faces and fluctuating pressures on each face all get their maximums when spacing ratio is 3. As height ratios change, the magnitudes of mean suction on windward face increase with height ratio, meanwhile, the magnitudes on other faces obtain their minimums as the height ratio is 1.0 and the spacing ratio is less than 3. The fluctuating pressures on the windward and side faces get their maximums and that on the leeward face reaches its minimum as the height ratio is 1.0. When the spacing ratio is greater than 3, mean pressures on each face decrease, while fluctuating pressures on the windward and side faces increase as the height ratio increases, and the fluctuating pressures on the leeward face get the minimum when the height ratio is 1.0.