The present invention provides an improved process for preparation of the substantially pure trazodone and its hydrochloride salt. The process comprises reaction of the compound-II (as described) with the compound-Ill (as described) optionally in the presence of an inorganic base, and a catalyst； wherein in the said process the trazodone free base and/or its hydrochloride salt are isolated by precipitation at lower temperature. The improved process for the preparation of trazodone hydrochloride (the compound I) provides the product with total amount of alkylating substances (as described herein) as impurity in less than 10 ppm. The improved process for the preparation of trazodone hydrochloride (the compound I) provides the product with total amount of l-(3-chlorophenyl)-4-(3-chloropropyl) piperazine as an impurity in less than 2.5 ppm.
