In law, a person only has one ground to petition for divorce, i.e. the marriage has broken down irretrievably.
Section 11A of the Matrimonial Causes Ordinance (Cap. 179 of the Laws of Hong Kong). In short, the Family Court will accept one or more of the following grounds as proof:
behaviour unreasonably bad
separation with (1 year) or without (2 years) consent to divorce
For a longer explanation, the Court shall not hold the marriage to have broken down irretrievably unless the applicant for divorce (i.e. the petitioner) satisfies the Court of one or more of the following facts:
spouse has committed adultery and you find it intolerable to live with your spouse;
spouse has behaved in such a way that you cannot be reasonably expected to live with your spouse; Usually it is a series of misconducts or intolerable behaviour. However, a single incident of grave misconduct is enough;
having lived apart for a continuous period of at least 1 year before filing the petition and that your spouse consent to a divorce;
having lived apart for a continuous period of at least 2 years immediately before filing the petition for divorce (in such a case your spouse's consent to a divorce is not required);
the other spouse has deserted you for a continuous period of at least 1 year immediately before filing the petition for divorce.