A method for determining a paging time slot during a period in which a base station is executing non-trunking service in a CDMA trunking system, wherein: when a base station can determine that a mobile station operates in a slotted mode and can determine a preferred slot cycle index of the mobile station, the smaller value of the preferred slot cycle index of the mobile station and a max slot cycle index are selected as a first slot cycle index, and the base station pages the mobile station with a slot cycle determined by the first slot cycle index; and when the base station cannot determine whether the mobile station operates in the slotted mode or not, or cannot determine the slot cycle index of the mobile station, the value of the slot cycle index is 1, the smaller value of the preferred slot cycle index of the mobile station and 1 is selected as a second slot cycle index, and the base station pages the mobile station with the slot cycle determined by the second slot cycle index; further wherein the preferred slot cycle index is determined by the following method: if the base station judges that a Push-To-Talk, PTT version number of the mobile station is greater than or equal to a predefined value, and if the base station has acquired a negative slot cycle index of the mobile station, then the smallest value of a max PTT slot cycle index, a PTT slot cycle index, a max slot cycle index and a slot cycle index is selected as the preferred slot cycle index; if the base station judges that the PTT version number is greater than or equal to the predefined value, and if the base station has not acquired the negative slot cycle index of the mobile station, then the base station selects the smallest value of the max PTT slot cycle index, the max slot cycle index and the slot cycle index as the preferred slot cycle index; if the base station judges that the PTT version number is smaller than the predefined value, then the base station selects the smaller value of the max slot cycle index and the slot cycle index as the preferred slot cycle index. when a base station can determine that a mobile station operates in a slotted mode and can determine a preferred slot cycle index of the mobile station, the smaller value of the preferred slot cycle index of the mobile station and a max slot cycle index are selected as a first slot cycle index, and the base station pages the mobile station with a slot cycle determined by the first slot cycle index; and when the base station cannot determine whether the mobile station operates in the slotted mode or not, or cannot determine the slot cycle index of the mobile station, the value of the slot cycle index is 1, the smaller value of the preferred slot cycle index of the mobile station and 1 is selected as a second slot cycle index, and the base station pages the mobile station with the slot cycle determined by the second slot cycle index; further wherein the preferred slot cycle index is determined by the following method: if the base station judges that a Push-To-Talk, PTT version number of the mobile station is greater than or equal to a predefined value, and if the base station has acquired a negative slot cycle index of the mobile station, then the smallest value of a max PTT slot cycle index, a PTT slot cycle index, a max slot cycle index and a slot cycle index is selected as the preferred slot cycle index; if the base station judges that the PTT version number is greater than or equal to the predefined value, and if the base station has not acquired the negative slot cycle index of the mobile station, then the base station selects the smallest value of the max PTT slot cycle index, the max slot cycle index and the slot cycle index as the preferred slot cycle index; if the base station judges that the PTT version number is smaller than the predefined value, then the base station selects the smaller value of the max slot cycle index and the slot cycle index as the preferred slot cycle index. if the base station judges that a Push-To-Talk, PTT version number of the mobile station is greater than or equal to a predefined value, and if the base station has acquired a negative slot cycle index of the mobile station, then the smallest value of a max PTT slot cycle index, a PTT slot cycle index, a max slot cycle index and a slot cycle index is selected as the preferred slot cycle index; if the base station judges that the PTT version number is greater than or equal to the predefined value, and if the base station has not acquired the negative slot cycle index of the mobile station, then the base station selects the smallest value of the max PTT slot cycle index, the max slot cycle index and the slot cycle index as the preferred slot cycle index; if the base station judges that the PTT version number is smaller than the predefined value, then the base station selects the smaller value of the max slot cycle index and the slot cycle index as the preferred slot cycle index.