High quality Yb3+ and Er3+ co-doped YCa4O(BO3)(3) crystals were grown by the Czochralski method. Phase relationships between y(3+)/yb(3+)/Er3+ and Ca2+/B3+ in the vicinity of the stoichiometric composition of YCa4O(BO3)(3) were discussed. The calculated absorption and emission cross sections were estimated. Efficient energy transfer from the excited Yb3+ to the Er3+ leads to strong emissions in the wavelength range of 1510-1580 nm peaking at 1535nm. Lifetime of Er-I-4(11/2) was measured to be 1.23ms. The energy transfer efficiency of 97% for Er0.02Yb0.2Y0.78Ca4O(BO3)(3) crystal was estimated from the reduced lifetimes of the Yb3+ - F-2(5/2) level.