Inclusion Criteria:  Men and women, aged 50-75 years Previously diagnosed with primary hypertension and has been taking antihypertensive medication within the past two weeks, OR has not been taking antihypertensive medication within the last two weeks but meets the following criteria for hypertension: on two separate (not on the same day) visits in a clinical setting, blood pressure measurements (average of 3 measurements each time) showed SBP≥140 mmHg and/or DBP≥90 mmHg; MTHFR 677 TT genotype (based on test results from the central laboratory in the screening period or a previous official test report from the laboratory with medical testing qualifications); Voluntarily participates and has given signed, informed consent.  Randomized-treatment phase inclusion criteria:  Good compliance during the run-in phase (assessed by a medical compliance survey for predicting patient compliance); Tolerance of amlodipine besylate 5.0mg tablets (does not result in discontinuation of medication due to adverse effects); No cardiovascular or cerebrovascular events occurred during the run-in phase; Voluntarily agrees to continue with participation in the study.  Exclusion Criteria:  Previously diagnosed secondary hypertension; Previously diagnosed stroke; Previously diagnosed myocardial infarction; Previously diagnosed heart failure; Cardio-cerebral-kidney revascularization and/or other large arterial stenting; Currently on dialysis, OR diagnosed with stage 4-5 chronic kidney disease, OR estimated glomerular filtration rate (eGFR) <30 mL/min/1.73m²; Known to have congenital (such as aortic stenosis) or acquired organic heart disease;  Known to have any of the following severe diseases or conditions:  a. Digestive system i. Previously diagnosed with any form of viral hepatitis that is currently still in the active phase; ii. Abnormal liver function test before enrollment (any of ALT, AST, GGT, TBIL, DBIL testing 3 times higher than normal, ALB ≤ 30g/L); iii. Subtotal gastrectomy and/or gastrojejunostomy; b. Respiratory system i. Previously diagnosed with pulmonary heart disease and/or chronic obstructive pulmonary disease; c. Presence of malignant tumors or other severe diseases;  Participant, at the investigator's discretion, is assessed to be unsuitable for the study, for reasons including but not limited to the presence of abnormal laboratory results, or clinical abnormalities/signs; Prior history of significant intolerance due to adverse reactions resulting from usage of amlodipine or other CCBs, candesartan or other ARBs, hydrochlorothiazide or other similar diuretics, or any drugs or health products containing folate or folic acid; Regular consumption of folic acid or compounds containing folic acid in the past 3 months;  Presence of any of the following conditions that could negatively influence a participant's ability to consent or participate in the trial:  Dementia; Severe mental disorders; Inability to express informed consent; Unlikely to complete the study follow-up as specified by the protocol, or plans to relocate outside of the study area in the near future; History of poor compliance when taking antihypertensive medications or is expected to have poor compliance during the study; Refusal to participate, or inability to modify current drug regimen; Within one month of the first visit, participating in any clinical trial for any drug that has yet to be officially approved by the state and is not currently approved for sale, OR currently participating in any clinical trial that could potentially impact the results of this study (medication use, drug efficacy, drug interaction, etc.)