bet LMi is a double-lined visual binary with an orbital period of similar to 39 yr. Via a simultaneous fitting to both astrometric and radial velocity measurements, we give a complete and improved orbit solution with high precision. Then, the component masses are precisely determined as 2.98 0.10Mand 1.92 0.04Mwith a relative precision of similar to 3%, respectively. The orbital parallax is determined to be 19.6 0.2 mas, which is two times more precise than Hipparcos parallax. With the known apparent magnitudes and magnitude difference of the components, we derive the luminosity of the components as 50.7 1.8Land 9.1 4.1L. The estimated radii of the components are 9.4 0.3Rand 3.7 1.5R.