He was born in Edinburgh, but spent his early youth at Dalmeny, where his father was for factor to the Earl of Rosebery; his mother was Mary Fyfe, of a Banffshire family.
After taking the course at Edinburgh University in arts and theology, he was, in 1842, ordained assistant and successor to John M. Robertson, minister of Livingston, Linlithgowshire.
At the disruption of 1843 he withdrew from the establishment, joined the newly formed Free Church, and for a time continued his ministry in the same parish.
Laing published the Catalogue of the Printed Books and Manuscripts in the Library of New College, Edinburgh, 1868.
He died before the work went to press; with the exception of the indices, it was arranged and edited by his elder surviving daughter, and appeared in four volumes entitled A Dictionary of Anonymous and Pseudonymous Literature of Great Britain, between 1882 and 1888.