Provided is a crystallization process of cyclic adenosine 3′,5′-monophosphate, which comprises the following steps: 1) reacting an aqueous solution of cyclic adenosine 3′,5′-monophosphate with a base to obtain a salt of cyclic adenosine 3′,5′-monophosphate; 2) reacting the cyclic adenosine 3′,5′-monophosphate salt solution obtained in step 1) with an acid to obtain cyclic adenosine 3′,5′-monophosphate; 3) keeping cyclic adenosine 3′,5′-monophosphate obtained in step 2) at 0-15° C.