In order to develop a broad-spectrum veterinary anthelmintic, a combined preparation of nitroxynil and levamisole was formulated for subcutaneous injection. The preformulation studies on solubilization, physicochemical stability and toxicity of combined preparation were performed. The combined preparation of nitroxynil-N-ethylglucamine and levamisole base could be solubilized up to 50.3%(w/v) of active ingredient concentration in propylene glycol/water system. Injectable solutions were most stable at $4^{circ}C$. Local toxicities such as flare and edema were not shown when the usual dose of the combined preparation was injected subcutaneously to the rats.