Pyroelectric properties of oxyborate crystals with monoclinic structure, including ReCa4O(BO3)3 (ReCOB, Re: rare-earth elements) and BiB3O6 (BiBO), were investigated by charge integration method. The pyroelectric p1 of ReCOB crystals was found to be negative, being on the order of -59.3∼-65.5μC/(m 2·°C) at 30°C, while the pyroelectric p3 was determined to be positive, being around 11.6∼31.0μC/(m 2·°C). The pyroelectric coefficients p1 and p3 for ReCOB crystals were observed to decrease with increasing temperature, with variations being on the order of -10.8% to -79.1% over the test temperature range of 20∼180°C. Comparing with ReCOB crystals, larger pyroelectric coefficient (p2) was obtained for BiBO crystals, being on the order of 105.0μC/(m2·°C) at room temperature, maintaining the similar value up to 180°C. Of particular interest is that ReCOB and BiBO crystals were found to possess relative high detectivity Fd, two to three times that of commercial TGS and LiTaO3.