This study consists of two parts: healthy subjects and chronic hepatitis B patients. Healthy subjects will conduct a single-dose, multiple-dose and food effect study.

I. Single-Dose Study：There will be a total of 6 dose cohorts（25 mg, 50 mg, 100 mg, 400 mg, 600 mg, 800 mg). 25 mg cohort as experimental cohort, plans to enroll 4 subjects (male or female) who will use HEC121120 tablets . The other else cohorts will include 10 subjects, of which 8 receives HEC121120 tablets and 2 receives placebo, regardless of gender. Each subject will only participate in one dose cohort. Each cohort will be divided into 2 group. The first group consists of 3 sentinels, two receiving active and one placebo. The second group will consist of the remainder of the cohort (6 active and 1 placebo) and, following review of the available safety data, will be dosed 24 hours after the sentinel group. Subjects can leave the pharmacy after their biological samples are collected on day 5. Subjects in each cohort will receive a single dose of HEC121120 or placebo in the fasted state on day 1, and safety evaluation is to be performed on day 2 and 5.

II. Food effect: There will be 1 dose cohort (200 mg), only to be admitted to the 100 mg dose cohort if a single dose has been completed and is safe and well tolerated. A total of 18 subjects were enrolled in this dose cohort, divided into two groups A and B (9 subjects in each group, 8 subjects in each group received HEC121120 and 1 received the placebo, with the ratio of male to female as close as possible. All subjects were required to participate in a single dose and food influence study on pharmacokinetics. Two cycles of cross-dose administration were performed, with a washout period of 7 days. Four sentinels were first enrolled in group A, and their safety indexes were evaluated by the investigator at least 24 h after administration. If tolerated, the remaining 5 sentinels could be enrolled in group A, and the remaining 4 sentinels could be enrolled in group B. The safety indexes were evaluated by the investigator at least 24 h after administration, if tolerated, the remaining 5 sentinels could be enrolled in group B.

III. Multi-Dose Study: There will be 1 dose(200 mg) cohort which will consist of 12 subjects, of which 10 receive HEC121120 tablets and 2 receive placebo, with the ratio of male to female as close as possible. All subjects will receive HEC121120 or placebo for 5 consecutive days (study doses, administration method (fasted or fed), dosing frequency, and dosing period are all to be determined based on data from the single-dose study and multiple-dose study). Subjects can leave pharmacy after their biological samples are collected. Safety evaluation is to be performed on day 3 and 7.

IV:Chronic hepatitis B patients: There will be a total of 3 dose cohorts (100、200、400 mg). Each cohort will consist of 14 subjects, of which 12 receive HEC121120 tablets and placebo(Entecavir simulation tablet), 2 receive Entecavir and placebo(HEC121120 simulation tablet). It is necessary to determine the administration method and dose for patients with chronic hepatitis B based on the results of the tolerance and PK study of healthy subjects. Each subject will only participate in one dose cohort.Initially, the drug frequency was set as once a day for 28 consecutive days. Safety and antiviral activity evaluation is to be performed on day 7, 14, 21±2, 29, 35±2.