Most dynamically confirmed stellar-mass black holes and the candidates were originally selected from X-ray outbursts . In the present work , we search for black hole candidates in the LAMOST survey by using the spectra along with photometry from the ASAS-SN survey , where the orbital period of the binary may be revealed by the periodic light curve , such as the ellipsoidal modulation type . Our sample consists of 9 binaries , where each source contains a giant star with large radial velocity variation ( \Delta V _ { R } \ga 70 ~ { } { km~ { } s ^ { -1 } } ) and periods known from light curves . We focus on the 9 sources with long periods ( T _ { ph } > 5 days ) and evaluate the mass M _ { 2 } of the optically invisible companion . Since the observed \Delta V _ { R } from only a few repeating spectroscopic observations is a lower limit of the real amplitude , the real mass M _ { 2 } can be significantly higher than the current evaluation . It is likely an efficient method to place constraints on M _ { 2 } by combining \Delta V _ { R } from LAMOST and T _ { ph } from ASAS-SN , particularly by the ongoing LAMOST Medium Resolution Survey .