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By analyzing two sets of complete $BVR_cI_c$ light curves of V342 UMa andthree sets of complete $BVR_cI_c$ light curves of V509 Cam, we determined thatthe two systems are both W-subtype contact binaries and that V342 UMa shows ashallow contact configuration, while V509 Cam exhibits a medium contactconfiguration. Since both of them are totally eclipsing binaries, the physicalparameters derived only by the photometric light curves are reliable.Meanwhile,the period changes of the two targets were analyzed based on all availableeclipsing times. We discovered that V342 UMa shows long-term period decreasewith a rate of $-1.02(\pm0.54)\times10^{-7}$ days/year and that V509 Camexhibits long-term period increase with a rate of $3.96(\pm0.90)\times10^{-8}$days/year. Both the conservative mass transfer and AML via magnetic stellarwinds can interpret the long-term period decrease of V342 UMa. The long-termperiod increase of V509 Cam can be explained by mass transfer from the lessmassive star to the more massive one. The absolute parameters of the twobinaries were estimated according to the Gaia distances and our derivedphotometric solution results. This method can be extended to other contactbinaries without radial velocities but with reliable photometric solutions. Theevolutionary states of them were discussed, we found that they reveal identicalproperties of other W-subtype contact systems.

Photometric investigations on two totally eclipsing contact binaries: V342 UMa and V509 Cam