Dusts and condensation which exist in the application of solar light pipes can affect daylighting performance. The influence of daylighting performance of solar light pipes by dusts and condensation was studied in this paper. Through measuring daylighting performance of skylight dome on different condensation conditions, it was proved that as the drop’s mean diameter from small to big, the transmitting efficiency is directly proportional to the drop’s mean diameter, and then is inversely proportional to a certain value. Through measuring the overall daylighting performance of solar light pipes on three different conditions—clean, dusts and condensation on sunny and cloudy days, the illuminance flux was obtained. The experimental results indicated that dusts and condensation worsen the daylighting performance of solar light pipes, and dusts had bigger influences than condensation.