The structures,spin reorientations,magnetic,and magnetostrictive properties of the polycrystalline Pr(Fe1 xCox)1.9 (x =0-1.0) cubic laves phase alloys between 5 K and 300 K are investigated.Large low-field magnetostrictions are observed at 5 K in the alloys with x =0.2 and 0.4 due to the low magnetic anisotropies of these two alloys.A large negative magnetostriction of about-1130 ppm is found in PrCo1.9 alloy at 5 K.The magnetizations of the alloys with 0 ≤ x ≤ 0.6 decrease abnormally at the spin reorientation temperature Tsr,and an abnormity is detected in the alloy with x =1.0 at its Curie temperature Tc (45 K).The substitution of Fe by Co increases the value of Tsr in the alloy with x value increasing from 0.0 to 0.4,and then reduces the value of Tsr with x value further increasing to 0.6.