Algol-type binary, as a subclass of binary, bears long time observation for its distinguished light curves. Long time observations of times of light minimum accumulate lots of information of Algol binaries. So we can recognize the variation of orbit period up to hundreds of years. This makes it a very good source to understand the corresponding physical mechanisms. In the present paper, the basic properties of Algol-type binary, the sorts of orbit period variation, corresponding mathmatic methods, the pysical mechanisms of period variation, are reviewed briefly. The structure equations of binary are studied also, the problem of structure can be viewed as one dimension in high approximation given the assumption of uniform rotation was discussed. The conservation of angular momentum of every layer of stellar mass was discussed. With the help of Virial theorem, the formula of angular velocity is deduced, and ennergy equilibrium equation is rewrited. Two Algol-type binaries(UW Vir and VW Hya) were studied based on the analyses of their O-C diagram, the variations of the orbital periods of them are obtained as follows: 1. The orbit period variation of Algol type binary UW Vir was analyzed. After collecting all possible times of light minimums, a continuous increase of orbit period was discovered at a rate of dP/dt=+1.37(\.01)*10-6days/year while it undergoes a cyclic period change with amplitude of 0.0397 days and a period of 62.3 years. The continuous increase of orbit period may be caused by a conservative mass transfer from less massive component to more massive one. Sinusoidal period oscillation indicates a third body with mass greater than 0.94Msun. Since no observational informations were reported about the third body, it may be a compactobject. 2. Base on the times of light minimum of Algol type binary VW Hya observed and collected, the orbit period of the binary is analyzed. It is discovered that the orbit period shows a continuous increase at a rate of dP/dt=+6.34(0.89)*10-7 days/year.Meanwhile, two period oscillations, with periods and amplitudes of 51.5 years, 0.0639 days and 8.75 year, 0.0048 days, respectively, were discovered. A conservative mass transfer from the less massive component to the more massive one at a rate of 7.89*10-8 Msun/year may be the reason that produce the period increation. The period oscillation may indicate two additional bodies with mass larger than 2.84Msunand 0.53Msunrespectively, and the more massive one may be a unseen neutron star or black hole candidate.
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