Background: In the patients with pulmonary embolism (PE), PE itself can cause haemoptysis and other reasons can also cause haemoptysis. Therefore, the clinical characteristics and the causes of haemoptysis are lacking. Methods: A retrospective analysis was performed that involved screening 583 PE patients and determining that haemoptysis occurred in 141 cases. Of these, eight cases were omitted due to anticoagulation-related haemoptysis or unavailable data, leaving 133 cases that were enrolled in final analysis (127 acute and 6 chronic case of PE). We classified the acute PE patients who combined with diseases which can cause haemoptysis to non-simple group (n = 61) and those without these diseases to simple group (n = 66). Results: The incidence of haemoptysis in PE patients was 23.75%. In the simple group, the amount of haemoptysis ≤ 5 mL was 80.30% (53/66) and ≤ 20 mL was 90.91% (60/66). In the non-simple group who combined with lung cancer, the amount of haemoptysis ≤ 5 mL was 68.4% (26/38) and ≤ 20 mL was 86.8% (33/38). Further analyses revealed that the amount of haemoptysis in the non-simple group was larger than that in the simple group (median 5 [5-125] vs. 5 [5-5], p < 0.001; volume ≥ 100 mL: 29.5% vs. 6.1%, p< 0.001). Among all the PE patients, chronic thromboembolic pulmonary hypertension (CTEPH), PE combined with tuberculosis (TB) and PE combined with bronchiectasis were independent risk factors for the amount of haemoptysis ≥ 100 mL (OR = 15.00, (95% CI: 2.235-100.652); 12.00, (3.101-46.437); 60.00, (6.552-549.441), respectively). Conclusions: The haemoptysis caused by acute PE or PE combined with lung cancer was mild and was characterised by blood in sputum. PE combined with TB, bronchiectasis and CTEPH are associated with moderate to massive haemoptysis, with a greater risk of haemoptysis ≥ 100 mL.