New light curves and photometric solutions of FP Lyn , FV CVn and V354 UMa are presented .
It is found that these three systems are W-subtype shallow contact binaries .
In addition , it is obvious that the light curves of FP Lyn and V354 UMa are asymmetric .
Therefore , a hot spot was added on the primary star of FP Lyn and a dark spot was added on the secondary star of V354 UMa .
At the same time , we added a third light to the photometric solution of FP Lyn for the final result .
The obtained mass ratios and fill-out factors are q = 1.153 and f = 13.4 \% for FP Lyn , q = 1.075 and f = 4.6 \% for FV CVn , q = 3.623 and f = 10.7 \% for V354 UMa .
The investigations of orbital period of these three systems indicate that the periods are variable .
FP Lyn and V354 UMa were discovered existing the secular increase component with a rate of dp / dt = 4.19 \times 10 ^ { -7 } d yr ^ { -1 } and dp / dt = 7.70 \times 10 ^ { -7 } d yr ^ { -1 } respectively , which are feasibly caused by the conservative mass transfer from the less massive component to the more massive component .
In addition , some variable components were discovered for FV CVn , which is a rate of dp / dt = -1.13 \times 10 ^ { -6 } d yr ^ { -1 } accompanied by a cyclic oscillation with amplitude and period of 0.0069 days and 10.65 yr .
The most likely explanation for the long-term decrease is angular momentum loss .
And the existence of an additional component is the most plausible explanation for the periodic variation .