Nylon 6 based magnetic pellets for injection molding were produced using plasma arc melt-spun $Nd_{10.5}Fe_{79}Co_{2}Zr_{1.5}B_{7}$ powders. Two sorts of bonded magnets made of two different sizes of particles ($38~75;mu extrm{m}$ and $75~150;mu extrm{m}$) were prepared to determine critical volume fraction of magnet powders, and the magnetic prop erties of the magnets were discussed as a function of density. For the nylon fi based Nd-Fe-Co-Zr-B pellets made of $38~75;mu extrm{m}$ particles, the critical volume fraction of powders 0.7 was obtained with the pellet density which is 90% of theoretical density while the magnets of $75~150;mu extrm{m}$ showed the density of 87% of the theoretical value with the same volume fraction. The nylon (i magnets with the addition of 0.5 wt. % silicon oil only exhibited the best magnetic properties to have $_{i}H_{c}=8.8;kOe,;B_{r}=5.1;kG$ and $(BH)_{max}=5.2;MGOe$ which are of world class. An empirical relationship in predicting the magnet density with a known fraction ($V_s$) of loading powders was obtained such as ${ ho}(g/cm^{3})=1.1+K.V_{s}$ where the K ranges over 5.3~5.6 be ing dependent upon the particle size loaded.