A bivariate rational interpolation spline with parameters was created in an earlier work which was based on function values only,and this spline is a rational one with biquartic numerator and biquadratic denominator.This paper discusses the spline’s boundary property,the approximation expression of the interpolation and the point control method of the interpolating surface.It is proved that the values of the interpolating function in the interpolation region are bounded no matter what the parameters might be,which is called the boundary proper...