We present the full VRI light curves and the times of minima of TY UMa to provide a complete photometric solution and a long‐term trend of period variation. The light curves show a high degree of asymmetry (the O'Connell effect). The maxima at 0.25 phase (Max I) are 0.021, 0.015, and 0.020 mag fainter than those at 0.75 phase (Max II) in V, R, and I, respectively. The period of TY UMa has varied in a sinusoidal way, superimposed on the long‐term upward parabolic variation. The secularly increasing rate of the period is deduced as 1.83 s per century (P˙/P=5.788×10‐10 d d‐1). The period of sinusoidal variation is about 57.4 yr. The spot model has been applied to fit the asymmetric light curves of TY UMa, to explain light variations. By changing only the spot parameters, the model light curves can fit the observed light curves for three epochs. This indicates that the variation of the spot location and size is the main reason for changing the shape of light curves, including two different maxima and the interchanging depths of occultation and transit minima.

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We have confirmed that the Mg ii h and k emission lines of SZ Psc are mainly enhanced by the K subgiant component of the system, using the radial velocities reduced from the emission lines. The intensity variation of the emission line is correlated with the orbital phase of SZ Psc. The shape of light curves of SZ Psc were changing every season. The three representative light curves of three different epochs, 1978, 1979 and 1981, were selected to find a unique solution of SZ Psc which can explain the variation of light curves. The binary parameters, including inclination, mass ratio, temperatures and potentials of both components for the three epochs coincide, although the shapes of light curves for three epochs are different from each other. Changing only spot parameters, the model light curves fit to the observed light curves for three epochs. This means that the variation of spot location and size is the main reason for changing the shape of light curves.

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