The relationship between the tensile properties and δ (delta) phase precipitation in cast alloy IN625 was investigated in this paper.Although the influences of δ phase on the mechanical properties have been pointed out in our previous work,the relationship is still not directly determined due to the coexistence of γ“ (gamma double prime) and δ precipitates.In order to exclude the effect from γ” phase,various fractions of δ precipitates with few γ\" precipitates were obtained by a set of experimental alloys aging at 750 ℃,and tensile tests were conducted in parallel.The results showed that both yield strength and ultimate tensile strength increased nearly in linear with increasing δ phase fraction,while the elongation was relatively and limitedly affected by δ precipitation when the area fraction of δ phase was above 10％.