A series of samples with composition (Tm1−xCax)Ba2 Cu 3Oy were prepared by the conventional solid‐state reaction method with 0 ⩽ x ⩽ 0.150. Unit cell a‐ and c‐axis increase and b‐axis decreases with increase of the amount of Ca substitution. As a result, orthorhombicity decreases as x increases. Both Tc and y decrease with x, whereas hole concentration (p/Cu) increases with increasing Ca content up to 0.34/Cu for x = 0.075 and then decreases dramatically with x. The highest Tc (89 K) is found for x = 0 sample.