Abstract: Abstract: Solar photovoltaic/thermal (PV/T) collectors using the heat pipe cooling technology are expected to be a new generation in the field of solar PV/T utilization, compared with the conventional flat plate. However, there are still two adverse operating conditions of PV/T systems in winter and summer. In summer, the photoelectric efficiency of the system decreases to be the lowest, while the photothermal efficiency reduces obviously, when the operating temperature reaches 75 ℃. In winter, the heat pipe loop starts to work late, due to the relatively weak solar radiation at low ambient temperature. Such working performance of the system can get worse under two adverse operating conditions, particularly in severe cold or tropical areas. In this study, a passive regulation was proposed to recycle the exhausted air from the air conditioning system, further to regulate the working temperature of solar photovoltaic/thermal collectors. In summer, the exhausted air was sent to the air layer between the absorber plate and the glass cover in the LHP-PV/T collector at the required water temperature. In winter, the exhausted air was sent to the air layer at sunrise. As such, the absorber plate was used to absorb the thermal energy from both the exhausted air and the solar radiation. Accordingly, the cycle of LHP started earlier, in order to improve the solar energy utilization efficiency of the system. A mathematical model of PV/T collector was established to explore the influence of system regulation on performances and circulation start of LHP using ANSYS Fluent software. Several assumptions were also proposed to simplify the model and reduce the amount of calculation, as well as some boundary conditions, such as the flow, thermal and momentum. The system operating performances were simulated before and after passive regulation, thereby compareing the influence of different regulation strategies on system performance. Additionally, a self-developed system outdoor was constructed to verify the accuracy of the model. A field test was also carried out under a typical working condition in summer in Qinhuangdao City, Hebei Province, China. Correspondingly, an outdoor test system was selected to operate in a relatively stable period, where the measured value was collected to compare with the simulated from 10:00 a.m. to 11:00 a.m. The simulation and test results show that the average relative errors were 0.02% and 0.47% for the water temperature and the solar thermal efficiency, respectively. The simulation and test results shows that the calculation accuracy of model was within the acceptable range of engineering design. Furthermore, the lower wind speed under the regulation mode was more conducive to the the heat pipe operation in summer, whereas, the higher wind speed greatly contributed improving the photoelectric efficiency of system. Different strategies of regulation demonstrated that the lower wind speed at the beginning of regulation mode contributed significantly to the solar thermal energy for better photoelectric efficiency of system. In winter, the regulation greatly advanced the starting time of LHP circulation, while the effective solar heat collection increased by 375.7% within half an hour after sunrise.