A two-stage photovoltaic thermal system based on solar trough concentration is proposed, in which the metal cavity heating stage is added on the basis of the PV/T stage, and thermal energy with higher temperature is output while electric energy is output. With the 1.8 m(2) mirror PV/T system, the characteristic parameters of the space solar cell under non-concentrating solar radiation and concentrating solar radiation are respectively tested experimentally, and the solar cell output characteristics at different opening widths of concentrating mirror of the PV/T stage under condensation are also tested experimentally. When the mirror opening width was 57 cm, the solar cell efficiency reached maximum value of 5.21%. The experimental platform of the two-stage photovoltaic thermal system was established, with a 1.8 m(2) mirror PV/T stage and a 15 m(2) mirror heating stage, or a 1.8 m(2) mirror PV/T stage and a 30 m(2) mirror heating stage. The results showed that with single cycle, the long metal cavity heating stage would bring lower thermal efficiency, but temperature rise of the working medium is higher, up to 12.06 degrees C with only single cycle. With 30 min closed multiple cycles, the temperature of the working medium in the water tank was 62.8 degrees C, with an increase of 28.7 degrees C, and thermal energy with higher temperature could be output. (C) 2014 Elsevier Ltd. All rights reserved.