The invention relates to a production method of a chemical product, particularly a production technique of guanidine hydrochloride, which comprises the following steps: mixing raw materials, and carrying out fusion reaction. The weight percent of the guanidine hydrochloride in the guanidine hydrochloride finished product is greater than 94%. By using ammonium carbonate instead of ammonia gas in the prior art as an assistant in the production process, the technique has the following advantages:1. the technique is simple and convenient for controlling technological conditions, and can lower the production cost by about 200 Yuan per ton;2. the quality of the product is greatly improved: the purity of the product obtained by the prior art is 88-92%, but the purity of the product obtained by the technique is high than 94%, which is a qualitative improvement for large-scale production; and 3. the safety in the production process is enhanced: the technique does not need liquid ammonia storage tanks, transmission pipelines and other dangerous facilities in the existing production process, thereby greatly enhancing the safety in the production process.