Polycrystalline ingots were synthesized by two-temperature zone method using P, Si, and Cd as the initial materials. Single crystals CdSiP2 with the size of 12 mm×40 mm and 15 mm×50 mm were successfully grown by self-seeding and seeded vertical Bridgman technique, respectively. The full width at half-maximum of the XRD rocking curve on (004) plane is 40″. The average transmittance of CdSiP2 crystal is 57% at 2-6.5 μm, which is close to its theoretical maximum. A small amount of transition metals, such as Fe, Cr, Mn and Ti, were detected in crystal by glow discharge mass spectrometry. The presence of Fe+ and Mn2+ was determined by electron paramagnetic resonance, which may cause optical absorption of the crystal in the near infrared band.